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Title: General Anatomy, Applied to Physiology and Medicine, Vol. 3 (of 3)

Author: Xavier Bichat

Translator: George Hayward

Release date: January 7, 2018 [eBook #56328]

Language: English

Credits: Produced by Sonya Schermann, Les Galloway and the Online
        Distributed Proofreading Team at http://www.pgdp.net (This
        file was produced from images generously made available
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                           GENERAL ANATOMY,

                              APPLIED TO

                       PHYSIOLOGY AND MEDICINE;

                           BY XAVIER BICHAT,

       PHYSICIAN OF THE GREAT HOSPITAL OF HUMANITY AT PARIS, AND
                 PROFESSOR OF ANATOMY AND PHYSIOLOGY.

                      Translated from the French.

                        BY GEORGE HAYWARD, M.D.

         FELLOW OF THE AMERICAN ACADEMY OF ARTS AND SCIENCES,
               AND OF THE MASSACHUSETTS MEDICAL SOCIETY.

                       _IN THREE VOLUMES._

                             VOLUME III.

                            _BOSTON_:
                   PUBLISHED BY RICHARDSON AND LORD.

                       J. H. A. FROST, PRINTER.
                                 1822.




DISTRICT OF MASSACHUSETTS, _to wit_:

  DISTRICT CLERK'S OFFICE.

BE IT REMEMBERED, that on the seventeenth day of April, A.D. 1822,
in the forty-sixth year of the Independence of the United States of
America, _Richardson & Lord_, of the said District, have deposited
in this office the title of a book, the right whereof they claim as
proprietors, in the words following, _to wit_:

"General Anatomy, applied to Physiology and Medicine; by Xavier Bichat,
Physician of the Great Hospital of Humanity at Paris, and Professor of
Anatomy and Physiology. Translated from the French, by George Hayward,
M. D. Fellow of the American Academy of Arts and Sciences, and of the
Massachusetts Medical Society. In three Volumes. Volume III."

In conformity to the Act of the Congress of the United States,
entitled, "An Act for the Encouragement of Learning, by securing the
Copies of Maps, Charts and Books, to the Authors and Proprietors of
such Copies, during the times therein mentioned:" and also to an Act
entitled, "An Act supplementary to an Act, entitled, An Act for the
encouragement of Learning, by securing the Copies of Maps, Charts and
Books, to the Authors and Proprietors of such Copies during the times
therein mentioned; and extending the Benefits thereof to the Arts of
Designing, Engraving and Etching Historical and other Prints."

  JOHN W. DAVIS,
  _Clerk of the District of Massachusetts._




MUSCULAR SYSTEM OF ORGANIC LIFE.


This system is not as abundantly spread out in the economy as the
preceding. The whole mass which it forms, compared with the whole of
the other, which is more than one third of the body, presents in this
respect a very remarkable difference. Its position is also different;
it is concentrated, 1st, in the thorax, where the heart and œsophagus
belong to it; 2d, in the abdomen where the stomach and intestines are
in part formed by it; 3d, in the pelvis where it contributes to form
the bladder and even the womb, though this belongs to generation, which
is a function distinct from organic life. This system then occupies
the middle of the trunk, is foreign to the extremities, and is found
far from the action of external bodies, whilst the other superficially
situated, forming almost alone the extremities, seems, as we have said,
almost as much destined in the trunk to protect the other organs, as
to execute the different motions of the animal. The head contains no
part of the organic muscular system; this region of the body is wholly
devoted to the organs of animal life.


ARTICLE FIRST.

OF THE FORMS OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

All the muscles of the preceding system take in general a straight
direction. These are all on the contrary curved upon themselves; all
represent muscular cavities differently turned, sometimes cylindrical
as in the intestines, sometimes conical as in the heart, sometimes
rounded as in the bladder, and sometimes very irregular as in the
stomach. No one is attached to the bones; all are destitute of
tendinous fibres. The white fibres arising from the internal surface of
the heart, and going to be attached to the valves of its ventricles,
have by no means the nature of the tendons. Ebullition does not easily
reduce them to gelatine; desiccation does not give them the yellowish
appearance of these organs; they resist maceration longer than them.

It is in general a great character that distinguishes the muscular
organic system from that of animal life, that it does not arise from,
nor terminate in fibrous organs. All the fibres of this last are
continuous either with tendons, or aponeuroses or fibrous membranes.
Almost all those of the first go on the contrary from the cellular
texture, and return to it after having run their course. I at first
thought that the dense and compact texture which is between the mucous
membrane and the fleshy fibres of the intestines, the bladder, the
stomach, &c. was an assemblage and net-work of many small tendons
corresponding to these fibres, and interwoven in the form of an
aponeurosis; the density of this layer deceived me at first view.
Ebullition, maceration, and desiccation have since taught me, that this
layer, completely foreign to the fibrous system, should be referred, as
Haller has said, to the cellular, which is only more dense and compact
there than elsewhere. It is this layer, which I have designated, in
the cellular system by the name of the sub-mucous texture. Many fibres
of the system of which we are treating appear to form an entire curve,
which is not crossed by any cellular intersection; some layers of the
heart exhibit this arrangement, which is in general very rare; so that
there is almost always an origin and termination of the fibres, upon an
organ of a nature different from their own.

We can hardly consider in a general manner the forms of the system of
which we are treating; each organ belonging to it is moulded upon the
form of the viscus to the formation of which it contributes. In fact,
the organic muscles do not exist in distinct fasciculi, like those of
animal life; all, except the heart, form but a third, a quarter and
often even less in the structure of a viscus.

The greatest number has a thin, flat and membranous form. There are
layers more or less broad, and hardly ever distinct fasciculi. Placed
at the side of each other, the fibres are rarely one above another;
hence it happens that occupying a very great extent, these muscles form
however a very small volume. The great gluteus alone would be larger
than all the fibres of the stomach, the intestines and the bladder, if
they were united like it into a thick and square muscle.


ARTICLE SECOND.

ORGANIZATION OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

The organization of the involuntary muscles is not as uniform as that
of the preceding. In these all is exactly similar excepting the
differences of the proportion of the fleshy fibres to the tendinous,
of the length of the first, of the prominence of the fasciculi,
of their assemblage into flat, long or short muscles; in whatever
place we examine them, their varieties are in their forms and not in
their texture. Here on the contrary, there is in this texture marked
differences; the heart compared with the stomach, the intestines with
the bladder are sufficient to convince us of this. It is by virtue of
these different textures, that the contractility and sensibility vary
as we shall see in each muscle, that the force of the contraction is
not the same, and that life is different in each, whilst it is uniform
in all those of animal life. We shall now consider in a general manner
the organization of the involuntary muscles.


I. _Texture peculiar to the Organization of the Muscular System of
Organic Life._

The organic muscular fibre is in general much finer and more delicate
than that of the preceding system; it is not brought into as thick
fasciculi. Very red in the heart, it is whitish in the gastric and
urinary organs. Besides, this colour varies remarkably. I have observed
that sometimes maceration renders it of a deep brown in the intestines.

This fibre never has one single direction, like that of the preceding
muscles; it is interlaced always, or found in juxta-position in
different directions; sometimes it is at a right angle that the
fasciculi are cut, as in the longitudinal and circular fibres of
the gastric tubes; sometimes it is with angles more or less obtuse
or acute, as in the stomach, the bladder, &c. In the heart, this
interlacing is such in the ventricles, that it is a true muscular
net-work. From these varieties of direction, results an advantage in
the motions of these sorts of muscles, which, being all hollow can by
contracting diminish according to many diameters the extent of their
cavity.

Every organic muscular fibre is in general short; those which, like
the longitudinal of the œsophagus, the rectum, &c. appear to run a
long course, are not continuous; they arise and terminate at short
distances, and thus arise and terminate successively in the same
direction or line; no one is comparable to those of the sartorius, the
gracilis, &c. as it respects length.

We know the nature of their fibres no better than that of those of
animal life; but they appear nearly the same under the action of the
different reagents. Desiccation, putrefaction, maceration, ebullition,
exhibit in them the same phenomena. I have observed upon the subject of
this last, that once boiled, the fibres of both systems are much less
alterable by the acids sufficiently weakened. After being some time in
the sulphuric, the muriatic and nitric diluted with water, they soften
a little, but keep their original form, and do not change into that
pulp to which raw fibres are always reduced in the same experiment. The
last of these acids turns them yellow as before ebullition.

I have also made an observation as it respects the horny hardening
which is produced the instant ebullition commences; it is this, that it
is always the same whatever may have been the antecedent dilatation or
contraction of the fibres. The stomach which at death was so dilated
as to contain many pints of fluid, is reduced to the same size, all
other things being equal, as that which is contracted so as to be no
larger than the cœcum. Diseases have a little influence on the horny
hardening. The heart of a phthisical patient exhibited to me in the
same experiment this phenomenon much less evidently, than that of an
apoplectic.

The resistance of the organic muscular fibre is in proportion much
greater than that of the fibres of the animal muscular system.
Whatever may be the distension of the hollow muscles by the fluid which
fills them during life, ruptures hardly ever take place in them.

The bladder alone sometimes exhibits this phenomenon, which is
however very rare in it. In the great retentions of the urine, in
which ruptures take place, it is almost always the urethra that is
ruptured, and the bladder remains whole. We meet in practice with a
hundred fistulas in the perineum, coming from the membranous portion,
to one above the pubis. We find in authors many examples of rupture of
the diaphragm; we know of but few of the rupture of the stomach, the
intestines and the heart.


II. _Common Parts in the Organization of the Muscular System of Organic
Life._

The cellular texture is in general much more rare in the organic
muscles than in the others. The fibres of the heart are in
juxta-position, rather than united by this texture. It is a little more
evident in the gastric and urinary muscles. It is almost wanting in the
womb; thus these muscles are not infiltrated, like the preceding, in
dropsies; they never exhibit that fatty state of which we have spoken,
and which sometimes loads the fibres. I have not observed in these
fibres the yellowish tinge which the others often take, especially in
the vertebral depressions.

The blood vessels are very numerous in this system; they are found
in it even in greater proportion than in the other; more blood
consequently penetrates them. This fact is remarkable, especially in
the intestines, in which the mesenteric arteries distribute numerous
branches, over an extremely delicate fleshy surface. But I would remark
that this appearance is to a certain degree deceptive, as many of these
vessels only traverse the fleshy surface to go to the mucous membrane.
In the ordinary state they give to the gastric viscera a reddish tinge,
which I have rendered at will livid and afterwards brought back to
its primitive state, by shutting and afterwards opening the stop-cock
adapted to the wind pipe, in my experiments upon asphyxia.

The absorbents and exhalants have nothing peculiar in this system.

The nerves come to them from two sources; 1st, from the cerebral
system; 2d, from that of the ganglions.

Except in the stomach in which the par vagum is distributed, the nerves
of the ganglions predominate everywhere. In the heart, they are the
principal; in the intestines, they are the only ones; at the extremity
of the rectum and the bladder, their proportion is greater than that of
the nerves coming from the spine.

The cerebral nerves intermix with them, in penetrating the organic
muscles. The cardiac, solar, hypogastric, plexuses, &c. result from
this intermixture which appears to have an influence upon the motions,
though we are ignorant of the nature of this influence.

All the nerves of the ganglions which go to the organic muscles, do not
appear to be exclusively destined to them. A great number of filaments
belong only to the arteries; such is in fact their interlacing, that
they form, as we have seen, around these vessels a real nervous
membrane, superadded to their own, and exclusively destined to them.
I would compare this nervous envelope to the cellular envelope which
is also found around the arteries, and which is wholly distinct from
the surrounding cellular texture; thus it only has communications with
the nerves of the organic muscles, without being distributed to these
muscles. Besides as the nerves of the ganglions are always the most
numerous and essential in them, and as their tenuity is extreme, the
nervous mass destined to each is infinitely inferior to that which
is found in the voluntary muscles. The heart and the deltoid muscle
compared together, exhibit in this respect a remarkable difference.


ARTICLE THIRD.

PROPERTIES OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

Under the relation of properties, this system is in part analogous to
the preceding, and in part very different from it.


I. _Properties of Texture. Extensibility._

Extensibility is very evident in the organic muscles. The dilatation of
the intestines and the stomach by aliments, by the extrication of gas,
by the fluids that are found there, that of the bladder by the urine,
by injections that are forced in, &c. are essentially owing to this
extensibility.

This property is characterized here by two remarkable attributes; 1st,
by the rapidity with which it can be put into action; 2d, by the very
great extent of which it is susceptible.

The stomach and intestines pass in an instant from complete vacuity
to great extension. Artificially distended, the bladder becomes
immediately of a size treble, quadruple even of that which is natural
to it. It sometimes however resists, but this does not prove its
defect of extensibility; it is because the fluid injected irritates
it and makes it contract; the organic contractility in exercise, then
prevents the development of extensibility, as it sometimes cannot be
brought into action by stimulants in a muscle laid bare, because the
animal contractility in exercise in the muscle, forms an obstacle to
it. The muscles of animal life are never capable of this rapidity in
their extensibility, whether because they are intersected by numerous
aponeuroses which dilate but slowly, or whether because their layers
of fibres are very thick, two circumstances that do not exist in the
muscles of organic life. Hence a remarkable phenomenon that I have
observed in all cases of tympanites. When we open the abdomen of
subjects that have died in this state, without wounding the swelled
intestines, these immediately burst out, swell more, and occupy twice
as large a space as they were contained in in the abdomen; why? Because
the parietes of the abdomen being unable to yield in proportion to the
quantity of gas that is developed, this has been compressed in the
intestines during life, and expands immediately by its elasticity when
the cause of compression ceases. In dropsies in which the distension is
slow, the abdominal parietes enlarge much more than in tympanites. The
size of the abdomen would be double in this, if the extensibility of
the parietes was in proportion to that of the intestines.

As to the extent of the extensibility of the organic muscles, we can
form an idea of it by comparing the empty stomach which oftentimes
is not larger than the cæcum in its ordinary state, with the stomach
containing sometimes five, six and even eight pints of fluid; the
bladder contracted and concealed behind the pubis, with the bladder
full of urine from suppression, rising sometimes even above the
umbilicus; the rectum empty, with the rectum filling a part of the
pelvis in old people in whom the excrements have accumulated in it; the
intestines contracted with the intestines greatly distended.

It is to the extent of extensibility of the organic muscles and to the
limits placed to that of the abdominal parietes, that must be referred
a constant phenomenon that is observed in the gastric viscera; viz.
that in the natural series of their functions, they are never all
distended at the same time; the intestines are filled when the matters
contained in the stomach are evacuated; the bladder is not full of
urine in the digestive order, until the other hollow organs are empty,
&c. In general, that is an unnatural order in which all the organs are
distended at once.

There is for the organic muscles a mode of extensibility wholly
different from that of which I have just spoken; it is that of the
heart in aneurisms, and the womb in pregnancy. The first, for example,
acquires a size double, treble even sometimes in its left side, and yet
it increases at the same time in thickness. This size is not owing to
distension, but to a preternatural growth. The aneurismatic heart is
to the ordinary heart, what this is to the heart of the infant; it is
nutrition that makes the difference and not distension; for whenever
it is owing to this it diminishes in thickness as it increases in
extent; there is no addition of substance. Besides the aneurismatic
heart has not often the cause that distends it, for commonly in this
case the mitral valves allow a free passage to the blood; whilst when
they are ossified the left ventricle often remains in a natural state.
Moreover, the slow progress of the formation of aneurism proves that
it is a preternatural nutrition that has presided over this increase
of the heart. You would in vain then empty this organ of the blood
it contains, it would not contract and resume its dimensions, as the
inflated intestine does which we puncture to allow the air to escape.

In the womb there are two causes of distension; 1st, the sinuses
greatly developed; 2d, an addition of substance, a real momentary
increase of the fibres of the organ which remains as thick and even
more so than in the natural state. At the time of accouchement, the
sinuses immediately flatten by the contraction of the fibres; hence
the sudden contraction of the organ. But as on the one hand nutrition
alone can remove by decomposition the substances added to the fibres to
enlarge them, and as on the other, this function is exerted slowly,
after the womb has undergone the sudden contraction owing to the
flattening of its sinuses, it returns but gradually and at the end of
some time to its ordinary size. Extensibility is not then brought into
action in the womb filled by the fœtus, and in the aneurismatic heart;
these organs really become at that time the seat of a more active
nutrition; they grow preternaturally, as they have grown naturally
with the other organs; but these do not then experience an analogous
phenomenon, they become monstrous in comparison. The womb decreases,
because the motion of decomposition naturally predominates over that of
composition after accouchement, whilst it was the reverse before this
period. The aneurismatic heart remains always so.

These dilatations of the heart should be carefully distinguished from
those really produced by extensibility, as in the right auricle and
ventricle for example, which are found full of blood at the moment
of death, because the lungs which are weakened, not allowing it to
pass through them, compel it to flow back to the place from which it
came. There are but few hearts which do not exhibit in very various
degrees, these dilatations, which we have the power in a living
animal of increasing or diminishing at will, according to the kind of
death we produce. Two hearts are hardly ever of the same size after
death; many varieties are met with, and these depend more or less on
the difficulties which the blood experiences in the last moments,
in passing through the lungs. Hence why in the diseases of the
heart, there is no standard by which we can compare the morbid size,
especially if we examine the organ as a whole. In fact the distension
of the right side can give it an aneurismatic appearance, and a size
even greater than that of some aneurisms. If we examine the left side
separately, the error is more easily proved, because this side is
subject to less variations. But the principal difference consists
in the thickness. The power of contraction appears to increase in
proportion to this thickness, which arises from the substance added by
nutrition. It is this power which produces the great beating that is
felt under the ribs, the strength of the pulse, &c.


_Contractility._

It is in proportion to extensibility. It is often brought into action
in the ordinary state. It is in virtue of this property, that the
stomach, the bladder, the intestines, &c. contract, and acquire a size
so small compared to what they have when they are full. In general,
there is no muscle of animal life, which is capable of such extreme
contractions as those of organic life.

It should be remarked, however, that life, without having contractility
immediately dependant upon it, since the intestines, the stomach, and
the bladder contract after death when their distension is removed,
modifies it in a very evident manner. The causes even which alter
or diminish the vital forces have an influence upon it; hence the
following observation that all those accustomed to open dead bodies can
make. When the subject has died suddenly, and the stomach is empty, it
is much contracted; when, on the contrary, death has been preceded by a
long disease which has weakened its forces, the stomach, though empty,
remains flaccid, and is found but very little contracted.

We should consider the substances contained in the hollow muscles of
organic life, as true antagonists of these muscles; for they have
not muscles that act in a direction opposite to theirs. As long as
these antagonists distend them, they do not obey their contractility
of texture; when they are empty, this is brought into action. It is
not, however, upon this property that the mechanism of the expulsion
of matters from these organs turns, as aliments from the stomach and
intestines, urine from the bladder, blood from the heart, &c. It is
the organic contractility that presides over this mechanism. It is
difficult to distinguish these properties in exercise. One occasions
a slow and gradual contraction, which is without the alternation of
relaxation; the other, quick and sudden, consisting in a series of
relaxations and contractions, produces the peristaltic motion, those
of systole, diastole, &c. It is after the organic contractility has
procured the evacuation of the hollow muscles, that the contractility
of texture closes them. In death from hemorrhage from a great artery,
the left and even the right side of the heart send out all the blood
they contain; afterwards empty, they contract powerfully, and the
organ is very small. On the contrary, it is very large when much blood
remaining in its cavities, distends it, as in asphyxia. These are the
two extremes. There are, as I have said, many intermediate states.

The contractility of texture is, in the system of which we are
treating, in proportion to the number of fleshy fibres. Thus, all
things being equal, the rectum, when empty, contracts upon itself with
much more force than the other large intestines; the contraction of the
ventricles is much greater than that of the auricles, and that of the
œsophagus is much greater than that of the duodenum, &c. &c.


II. _Vital Properties._

They are almost in an inverse order of those of the preceding system.


_Properties of Animal Life. Sensibility._

The animal sensibility is slight in the organic muscles. We know
the observation related by Harvey upon a caries of the sternum that
laid bare the heart; they irritated, without its being felt by the
patient, this organ, which only contracted under the stimulant. Remove
the peritoneum behind the bladder of a living dog, and irritate the
subjacent muscular layer, the animal gives but few marks of pain. It
is difficult to make these experiments upon the intestines and the
stomach; their muscular coat is so delicate that we cannot act upon it
without at the same time stimulating the subjacent nerves.

It appears that the organic muscles are much less susceptible of the
feeling of lassitude, of which the preceding become the seat after
great exercise. I do not know however if in those to which many
cerebral nerves go, it does not take place; for example, when the
stomach has been for a long time contracted, it is probable that the
lassitude of its fibres, produces in part the painful sensation that
we then have, and which we call hunger, a sensation that should be
distinguished from the general affection that succeeds it, and which
becomes truly a disease, when abstinence has been too much prolonged.
We know that substances not nutritive then appease this sensation
without remedying the disease, when the stomach is filled with them.
I refer to the same kind of sensibility the anxiety and distress
which patients experience, in whom we keep the bladder in permanent
contraction by an open sound in the urethra, which transmits the urine
as fast as it falls from the ureters. This sensation does not resemble
that of hunger, because the sensibility of the bladder and that of
the stomach being different, their modifications cannot be the same.
Thus each of these two sensations is different from that of which the
muscles of animal life, for a long time contracted, become the seat. I
do not believe that the sensation of hunger belongs solely to the cause
I have pointed out, and which others have not spoken of; but it cannot
be denied that it has much part in it. Who knows if, after a fever in
which the action of the heart has been for a long time accelerated,
the weakness of the pulse which accompanies convalescence, is not a
sign of the lassitude in which its fleshy fibres are, on account of the
antecedent motion? We know the painful sensation of fatigue which the
stomach experiences after the contractions of vomiting.


_Contractility._

The animal contractility is foreign to the muscles of organic life.
To be convinced of this, we must recollect that on the one hand this
contractility always supposes the influence of the brain and the
nerves, to bring in play the action of the muscle, and that on the
other, the brain, in order to exert this influence, must be excited
by the will, by stimulants or by sympathies. Now none of these causes
acting upon the brain, the organic muscles cannot contract.

Every body knows that these muscles are essentially involuntary. If
some men have had the faculty of arresting the motions of the heart,
it is not upon this organ that the brain has acted; the action of the
diaphragm and the intercostals has first been suspended; respiration
has ceased for a time; then consequently the circulation.

If we irritate the brain with a scalpel or any other stimulant, the
muscles of animal life become convulsed; they are paralyzed if we
compress this organ. Those of organic life, on the contrary preserve in
both cases their natural degree of motion. The heart still continues
to beat, the intestines and stomach move some time after the cerebral
mass and spinal marrow have been taken away. Who does not know that
the circulation goes on very well in acephalous fœtuses; that after
the blow that has knocked down an animal, and rendered his whole
voluntary muscular system immoveable, the heart is still for a long
time agitated, the bladder rejects the urine, the rectum expels the
excrements, &c. the stomach even sometimes vomits up aliments? Opium,
which benumbs the whole animal life, because it acts especially
upon the brain which is the centre of it, which paralyzes all the
voluntary muscles, leaves the others unaffected in their contractions.
Intoxication produced by wine exhibits the same phenomenon. A man
staggers after drinking; his limbs refuse to carry him, and yet his
heart beats with force; his stomach often heaves and rejects the
surplus fluids it contains. All narcotic substances also produce this
effect.

If from experiments we pass to observations on the sick, we see that
all cerebral affections are foreign to the organic muscular system.
Wounds of the head with depression, fungi of the brain, effusions of
blood, pus and serum, apoplexy, &c. affect exclusively the voluntary
muscles, the action of which they increase, weaken or destroy. In the
midst of this general derangement of animal life, the organic remains
unaffected. The paroxysm of mania and malignant fever likewise proves
this fact. Who does not know that in this last the pulse is oftentimes
scarcely altered, that sometimes even it is slower?

Frequently in diseases of the head, there are spasmodic vomitings; the
action of the heart is accelerated in cerebral inflammations, &c. But
these are sympathetic phenomena which happen in the organic muscles, as
they do in all the other systems; they may not appear nor be developed;
a thousand irregularities are observed in their progress. Whereas
the contraction of the muscles of animal life by affections of the
brain is a constant, invariable phenomenon, which nothing disturbs,
and the development of which nothing prevents, because the means of
communication are always the same between the affected organ and the
one that moves.

If in the examination of the phenomena relative to the cerebral
influence upon the organic muscles, we follow an inverse order, that
is to say, that in the affections of these muscles we examine the
state of the brain, we observe the same independence; consider most
vomitings, the irregular motions of the intestines which take place in
diarrhœas, those especially which form the iliac passion, &c. observe
the heart in the agitations of fevers, in the irregular palpitations
of which it becomes frequently the seat, &c. in these derangements
of the organic muscles, you will very seldom find signs of lesions of
the cerebral organ; it is calm, while every thing is disordered in
organic life. Cullen thought that in syncope the action of the brain
ceased first, and that that of the heart was afterwards consequently
suspended. It is precisely the reverse in the greatest number of cases.
The heart, at first affected, ceases to act; now its action being
essential to that of the brain, whether from the motion it communicates
to it, or from the red blood it sends, the functions of this last are
suddenly suspended and the whole animal life ceases. This is remarkable
especially in the syncopes that arise from the passions, in those from
hemorrhages, polypi, great evacuations, &c. I refer upon this subject
to my Treatise upon Life and Death.

If from the influence of the brain we pass to that of the nerves, we
find new proofs of the absence of animal contractility in the organic
muscles. The most of these muscles receive, as we have seen, two
species of nerves, the one cerebral, the other from the ganglions.

The heart, the stomach, the rectum and the bladder are evidently
entered by the first species of nerves; now by cutting, or irritating
in any way the cardiac filaments of the par vagum, the heart
experiences no alteration from it; its motion is neither retarded, nor
accelerated. The division of both branches of the par vagum is fatal,
it is true, but not until after some days; and I doubt whether it is by
the heart that death commences in this case. The principal phenomena
consequent upon this division show a great embarrassment in the lungs,
a great difficulty of breathing; the circulation appears to be troubled
only in consequence.

The same nerves going to the stomach, the same experiment serves to
prove the cerebral influence upon this viscus. Now the division of that
of one side is usually nothing upon it; that of both soon produces a
remarkable derangement in it. But this derangement is wholly different
from that which follows the section of the nerve of a muscle of animal
life, which becomes suddenly immoveable, whilst that on the contrary
the stomach not communicating with the brain except by the par vagum,
seems to acquire in an instant an increase of power; it contracts
and hence the spasmodic vomitings that are almost always observed
during the two or three days that the animal survives the experiment,
vomitings that I have constantly noticed in dogs, and which Haller and
Cruikshank had before observed. It appears then from this, that though
the brain has a real influence upon the stomach, this influence is of
a nature wholly different from that which it exerts upon the voluntary
muscles. I would observe however that the irritation of one branch of
the par vagum, or of both, makes the stomach immediately contract,
as happens in a voluntary muscle when we irritate its nerve. It is
necessary, in order to make this experiment, to open the abdomen of a
living animal, and afterwards to irritate the eighth pair in the region
of the neck, so as to have in sight the organ that we make contract.

The bladder and the rectum appear to approximate the voluntary muscles,
in their relation with the brain, more than the stomach and the heart.
We know that falls on the sacrum, from which arises a shock of the
inferior part of the spinal marrow, produce retention of urine; that
they strike, as it were, this organ with the same paralysis as the
inferior extremities, which then also cease to move. Yet as the bladder
is very powerfully assisted in its functions by the abdominal muscles,
by the levator ani and other voluntary muscles which surround it, the
immobility of these muscles contributes much to the inability to
evacuate the urine. That which makes me think so, is that, 1st, the
irritation of the spinal marrow towards its inferior part which puts in
motion all the voluntary muscles of the inferior extremities and of the
pelvis, does not produce any effect upon this part. I have convinced
myself of this fact many times upon dogs and guinea-pigs. 2d. By
irritating the nerves coming from the sacral foramina and going to the
bladder, nerves that it is often very difficult to find, on account of
the blood in an animal recently killed, I have seen this muscle remain
immoveable. On the contrary all these nerves having been cut, the
injection of a fluid slightly stimulant makes it contract with force.
3d. In experiments upon living animals, as in surgical operations, the
violence of the pain which sometimes produces spasmodic contractions
of all the muscles of animal life, frequently occasions an involuntary
discharge of urine. Now in these cases it is not the bladder that
is convulsed; for if in an experiment this phenomenon takes place,
open the abdominal parietes, in an instant the flow of urine ceases,
because on the one hand the muscles of these parietes cannot act upon
the intestines and press them against the bladder, and because on the
other the levator ani which contracts and raises this organ, has no
resisting point against which it can compress it above. Observe in
fact that in strong jets of urine, the bladder is placed between two
opposite efforts, one superior, which is the gastric viscera pressed by
the diaphragm and the abdominal muscles, the other inferior, which is
especially the levator ani which acts by contracting from below above,
whilst the opposite effort acts from above below; now these two efforts
are evidently under the cerebral influence. I have very frequently
had occasion to observe the bladder full of urine in a living animal
whose abdomen was opened; I have never seen it contract with sufficient
violence to expel the fluid.

I do not deny but that the bladder, by the nerves it receives from the
sacral plexuses, is to a certain extent a voluntary muscle; but I say
that it is principally by forces accessory to its own and necessary
to its functions, that it is subjected to the will; that the animal
contractility is much greater in its functions than the sensible
organic contractility. How then is the urine retained in this organ,
or expelled from its cavity at will? In this way; when the urine falls
into the bladder, and is there on the one hand but a short time,
and on the other only in small quantity, it is not then an irritant
sufficiently powerful to produce the exercise of the sensible organic
contractility. The effort which the bladder makes is so small, that it
cannot overcome the resistance of the urethra, which being shut by the
contractility of texture, must be dilated by the impulse communicated
to the urine. In order to void this fluid, there must then be added
to the contraction of the bladder that of the surrounding voluntary
muscles; now the least effort of these muscles is sufficient to
overcome the resistance of the urethra. But if the urine is in great
quantity in the bladder, and it has acquired by remaining in it a
long time that deep colour which indicates the concentration of its
principles, then the irritation that it produces on the organ brings
powerfully into action the sensible organic contractility; the bladder
contracts, and in spite of the animal, there is an evacuation of urine.

In the rectum, in which the excrements have not a long canal, but only
a simple opening to pass, this is furnished with a sphincter which
is wanting in the urethra. This sphincter habitually closed must be
dilated by the impulse communicated to the excrements. When they are
in the rectum a short time and in small quantity, the sensible organic
contractility is not brought into action with sufficient power to expel
them; it requires the action of the neighbouring voluntary muscles.
If this action is not determined by the influx from the brain, the
excrements remain in the intestines; hence how, for some time, we
retain them at will. But as they increase in quantity, and become
more acrid by remaining and consequently more irritating, then the
sensible organic contractility strongly brought into action, empties
the intestine involuntarily. If the sphincter, which is voluntary, is
paralyzed, there will be incontinence, because no resistance is opposed
to the tendency of the rectum to contract, a tendency which though
feeble as long as it is but partly filled, is however always real.

From what we have said, it appears evidently that the bladder and
rectum, though receiving cerebral nerves, are yet less influenced by
the brain than it at first view appears, and that there is evidently
between them and the voluntary muscles a very great difference. They
are not mixt, as it is called; they approach the organic muscles
infinitely nearer than the others; I doubt even whether if no accessory
power acted with and compressed them, the mind could by the nerves
which come from the sacral plexuses, make them contract at will. I have
never seen an animal void his excrements when the abdomen was open.

Let us conclude from all that has been thus far said, that the cerebral
nerves which go to the organic muscles have upon them an influence
which by no means resembles that of the cerebral nerves going to the
muscles of animal life. I am ignorant moreover of the nature of this
influence.

All the organic muscles receive nerves from the ganglions, both the
preceding ones which are also penetrated by the cerebral nerves, and
the small intestines, and the cœcum, colour, &c. which are exclusively
pervaded by them. Now by cutting, tying or irritating in any manner
these nerves, by stimulating the ganglions from which they go, by
destroying or burning them with a concentrated acid or alkali, the
muscle remains in its natural state; its contractions are neither
accelerated nor retarded.

I have not been contented with ordinary agents in convincing myself
of the deficiency of real action of the nerves upon the organic
muscles; a fact, which all good physiologists have always admitted,
notwithstanding the opinions hazarded by some physicians who apply the
vague term of nervous influence to organs which are not susceptible of
it.

I have then employed galvanism, and I am convinced that it has very
little, almost no power, in putting into action muscular contractions
in organic life, whilst it is the most powerful agent in animal life.
I shall not here relate my experiments upon this subject; they will be
read in my Researches upon Death.

We can conclude from all that precedes, that the cerebral and nervous
influence upon the organic muscles is not known to us; that it does
not act as upon the voluntary muscles. It is however real to a certain
extent, since it is necessary that the nerves which enter into the
composition of these muscles should be of some use; but we are ignorant
of this use.


_Organic Properties._

The organic sensibility is strongly characterized in the muscles of
which we are treating. Before the sensible organic contractility is
developed in them, it is necessary that this should be put in action.
But as these two properties are not separated, as in their exercise
they always succeed each other, what we are going to say of sensible
organic contractility will apply also to the sensibility of the same
nature.

Insensible organic contractility or tone, exists in the muscular
system, to a degree necessary for its nutrition; but it does not
exhibit in it any thing peculiar.

It is the sensible organic contractility that is the predominant
property in this system, all the functions of which rest almost
entirely upon this contractility, as all the functions of the preceding
muscular system are derived as it were from the animal contractility.
We shall now examine more in detail this essential property, with
regard to which physiology owes so much to the illustrious Haller. We
can consider it in three relations; 1st, in the stimuli; 2d, in the
organs; 3d, in the action of the first upon the second.


_Of the Sensible Organic Contractility considered in relation to
Stimuli._

Stimuli are natural or artificial. The action of the first is continual
during life; upon them turn in part the organic phenomena; they place
in action the muscles, which without them would be immoveable; they are
as it were to these organs what pendulums are to our machines; they
give the impulse. The second can hardly have effect until after death,
or in our experiments.


_Natural Stimuli._

These stimuli are blood for the heart, urine for the bladder, aliments
and excrements for the gastric organs. Every organic muscle has a body,
which, habitually in contact with it, supports its motions, as every
animal muscle habitually in relation with the brain, borrows from it
its power of motion. The natural stimuli support the organs at the
same degree of mobility while they remain the same. All things being
equal on the part of the organs, the pulse does not vary, the digestive
periods continue for the same length of time, the intervals between
the excretion of urine are equal, whilst the blood, the chyle or the
urine exhibit no differences. But as these substances experience an
infinite number of varieties, the organs preserving the same degree of
sensibility, have yet frequent changes in their motion.

At the instant chyle enters the blood during digestion, the pulse
changes, because the heart is differently irritated. We observe the
same phenomenon under different circumstances; 1st, in re-absorptions
in which pus goes into the mass of blood; 2d, in the injection of
different fluids in the veins, injections that were so frequently
made in the last age, at the period of experiments upon transfusion,
and which I have also had occasion to make with other views which I
shall mention; 3d, in inflammatory diseases in which the blood takes a
peculiar character that is yet but little known, and which occasions
the formation of the pleuritic buff; 4th, in various other affections,
in which the nature of this fluid is remarkably altered; 5th, in the
passage of the red blood into the system with black blood. I have
observed that in putting a curved tube into the carotid of one side
and the jugular of the opposite of a large dog, so that one forces
blood into the other, the passage of the red blood into the veins is
not fatal like that of the black blood into the arteries; but there is
almost always at first an acceleration of the motions of the heart.

The influence of the degeneracy of the fluids in diseases has no doubt
been exaggerated; too frequent a source of morbid derangements has
been placed in this portion of the economy. But it cannot be denied,
that according to the different alterations that the fluids exhibit,
they may be capable of exciting differently the solids that contain
them. We know that in the same individual, and with the same mass of
aliments, digestion varies from one day to another in the duration of
its periods; that some aliments prolong and others accelerate it; that
some remain very long in the stomach, as it is said, and others as it
were only pass through it. Now in all these cases the organ remains
the same, the fluid only varies. According as the kidney secretes
urine more or less acrid and consequently more or less irritating, the
bladder retains it for a longer or shorter time. Such is oftentimes
its stimulating qualities, that the moment it comes into this organ
it is involuntarily rejected. Shall I speak of emetics and evacuants
by the intestinal canal, the effects of which are so variable? We
know that the words drastic, purgative, laxative, &c. indicate the
different degrees of the stimulating qualities which certain substances
introduced into the alimentary canal exhibit, degrees which are to be
considered abstractedly from those of the sensibility of the organs;
this in fact can be such, that a laxative may produce greater effects
than a drastic purge.

Not only the quality, but also the quantity of the fluids contained in
the organic muscles, has an influence upon their contractility. 1st.
The word plethora is certainly employed too loosely in medicine; but we
cannot doubt that the state which it expresses sometimes exists; now
the more blood there is in the heart, the more are its contractions
accelerated. 2d. I have many times made transfusion in dogs, whether
with a view to that alone, or in researches relative to respiration
and circulation. Now I have always observed, that by not opening a
vein, to empty the blood as fast as the external jugular receives it
(for I always choose this vein for the experiment) by thus producing
consequently an artificial plethora, I have, I say, always observed
that the motion of the heart was accelerated. I have even seen the
eye of a dog become bright and as it were inflamed; in others this
phenomenon has not been observed. 3d. We know that in running, in
which all the muscles by contracting press out from all sides the
venous blood contained in their texture, this which enters the heart in
abundance, makes it palpitate powerfully. 4th. There is not doubt but
that the quantity of urine and excrements as much and more than their
quality, is for the bladder and the rectum, a cause of involuntary
contraction. 5th. We know the serious consequences that arise from
giving emetics and cathartics in too large doses. 6th. A glass of tepid
water often does not produce vomiting when a pint will bring it on
powerfully, &c. &c.


_Artificial Stimuli._

The artificial stimuli are in general all the bodies in nature. Such
is in fact the essence of organic contractility, that a muscle because
it is in contact with a body to which it is not accustomed, instantly
contracts. If the muscles are not irritated by the organs that surround
them and with which they are in relation, it is because habit has
blunted the sensation which arises from this relation. But when these
organs change their modifications, when extracted from the body of the
animal, they become cold, and are afterwards applied to the organic
muscles laid bare, they will make them contract.

Caloric, by its absence which constitutes cold, as by its presence from
which arises heat, can equally excite the muscles and in general all
the organs. At the instant we open the thorax or the pericardium of a
living animal, the heart is agitated with a suddenly increased force;
it is because the air acts upon it, and it passes from the temperature
of the body to another which is different. All the aeriform fluids,
light, all fluids, &c. are stimuli of the muscles. If we see the heart
emptied of blood, the stomach and intestines deprived of the substances
that ordinarily enter them, contract with more or less force when they
have been taken out of the body, it is because the surrounding medium,
and the substances with which it is charged, contribute to produce this
effect; they are then the stimuli of these organs.

In general the artificial stimuli act in different ways; 1st, by their
simple contact; 2d, by tearing or cutting mechanically the fibres; 3d,
by tending to combine with them; 4th, there are some of whose mode of
action we are completely ignorant; such for example is electricity.

When the stimuli act only by simple contact, the fluids are, all things
being equal, more efficacious than the solids, because they stimulate
by a greater number of points; as they irritate not only the surfaces
of the organ, but penetrate also into the interstices of the fibres.
The solids produce an effect in proportion to the extent of their
excitement, to the greater or less pressure that they exert, to their
density, their softness, &c. They are almost always fluid substances
that nature employs for stimuli in the ordinary state.

Tearing is a mode of excitement more active than contact. The heart,
the intestines often inert when they are only touched by the scalpel,
contract powerfully when the point of it excites them. Cutting produces
a less sensible effect than tearing. Cut transversely, the fibres
oscillate and are agitated only by the sensible organic contractility,
whilst by the contractility of texture they experience an evident
retraction.

Chemical excitement is, in the greatest number of cases, the most
advantageous; but it is necessary here to distinguish that which
belongs to the horny hardening, from that which is the effect of
irritability brought into action. 1st. Plunge a frog without skin and
alive into a concentrated acid; instantly every thing is disorganized;
the reagent acts so strongly, that we can distinguish neither horny
hardening nor contractility. 2d. Weaken the acid a little and plunge
into it, the inferior extremities only of a frog; in an instant they
stiffen by the contraction of the extensors, which overcome the
flexors; for in this experiment, this is almost a constant phenomenon;
withdraw the animal; its thighs remain immoveable, life has been
extinguished in them; the contraction that has come on is a horny
hardening, and not a vital phenomenon. A dead frog plunged into the
same liquor experiences the same phenomenon. 3d. Weaken the acid still
more; the instant the animal is plunged into it its limbs contract; but
relaxation succeeds the contractions; these are alternate motions; it
is the irritability that begins to be put into action. Yet if the acid
is not very weak, some marks of the horny hardening still remain, and
the animal has a stiffness in the motions of the inferior extremities,
the evident result of the first degree of this horny hardening. 4th.
Finally, if the acid is very weak, it becomes a simple irritant which
puts in action the sensible organic contractility, without altering
the texture of the fibres; the animal after coming out of the fluid
preserves the same power of motion.

These experiments which it would be easy to multiply upon animals with
warm blood, but which I have never attempted upon them, evidently show
what belongs to the horny hardening, and what is the effect of vital
contraction. Yet there is not an exact limit between them, and there is
one degree of weakness of the acid in which these two causes of motions
are confounded.

There is a mode of excitement to which authors have not paid attention;
it may be called negative; it is that of which I spoke just now on the
subject of caloric, the privation of which is oftentimes a very active
stimulant. In the different experiments that I have had occasion to
make, this has frequently struck me. Apply a stimulant to a muscle, it
contracts; but at the end of some time the motion ceases, though the
contact continues; remove the stimulant, the motion frequently returns
in an instant. In general, nothing is more common in the heart, the
intestines, &c. than their contractions ceasing under the continued
action of a stimulant, and returning instantly upon its absence. I
confess that this phenomenon is not as invariable and constant as that
of the contraction produced by the application of the stimulus which
succeeds a state of non-excitement; but this happens very often. We
might say that the organic sensibility is in this case like the animal,
that every new state affects it, whether it be positive or negative.
The passage from non-excitement to excitement is more lively; but the
opposite passage is not less when it is sudden. Moreover this manner
of describing the sensible organic contractility in exercise, deserves
some further experiments.


_Of the Sensible Organic Contractility considered in relation to the
Organs._

The sensible organic contractility, considered in the organ in which it
has its seat, exhibits numerous varieties which are relative; 1st, to
the diversity of texture; 2d, to age; 3d, to sex; 4th, to temperament,
&c.


_First Variety. Diversity of the Muscular Texture._

The animal contractility is everywhere the same in the voluntary
muscles, because their organization is uniform. All things being equal
as to the number and length of the fibres, the phenomena of contraction
are exactly the same everywhere; here, on the contrary, the varieties
of texture inevitably produce varieties in the vital properties.

Each involuntary muscle is at first especially in relation with
the fluid which ordinarily acts as its stimulus. The blood alone
can regularly support the motions of the heart. Let this fluid be
altered in any manner, the contractions become irregular. All foreign
substances forced into the veins produce this phenomenon. The urine,
which supports with harmony the motions of the bladder, would disturb
those of the heart, if it circulated in its cavities. The blood,
more soft in appearance than the urine, can agitate convulsively the
bladder, if it happens to be in it. I took care with Desault of a
patient affected for a long time with retention of urine, and whom
he had cut for a very large stone. After the operation, the urine
remained stagnant in the bladder as long as it was alone, but when a
little blood entered this organ, it contracted involuntarily and the
bloody urine was evacuated. The excrements, which could continue for
a long time in the rectum without making it contract, would make the
stomach heave in an instant, &c. All these phenomena are to be referred
to varieties of sensibility of the mucous membranes, varieties which we
shall notice again. They prove evidently that each muscle has a degree
of organic contractility which is peculiar to it, and that this or that
fluid of the economy can exclusively, in a natural state, put it in
exercise in a regular manner.

Foreign fluids exhibit the same result; the emetic which makes
the stomach contract, is injected with impunity into the bladder;
purgatives do not produce vomiting, &c. This relation of foreign fluids
with the sensible organic contractility takes place, whether, as in
the preceding case, these fluids are applied to the mucous surfaces
corresponding to the muscles, or whether they come to the muscles by
the circulation, as the experiments have proved which were made in the
last age upon the introduction of medicinal substances into the veins;
experiments of which Haller has collected a great number of results.
We have seen in these experiments, the circulation present to all the
organs sometimes an emetic, and the stomach alone contracts; sometimes
a purgative, and the intestines only enter into action, &c. Taken
in by cutaneous absorption, medicinal substances occasion the same
phenomenon. Applied by friction, purgatives, emetics, &c. do not make
all the organic muscles contract, though the circulation presents them
to all, but only those with which their sensibility is in relation.

In the various affections of which they are the seat, we see the
organic muscles having each a peculiar mode of irritation answer to
each stimulus, and remaining deaf, if we may so say, to the voice of
the others.


_Second Variety. Age._

Age modifies wonderfully the sensible organic contractility. In
infancy it is very evident; the muscles answer with extreme ease to
the stimuli; the bladder retains the urine with difficulty; children
void it in sleep involuntarily; the heart contracts with a rapidity of
which the pulse is the measure; all the digestive phenomena are more
prompt; hence there is less interval between the returns of hunger. It
is a phenomenon analogous to that of the voluntary muscles, in which
the rapidity of the motions is found, in the first age, connected with
their small degree of force.

After infancy, the susceptibility of the muscles to answer to their
stimuli, is constantly diminishing; thus all the great phenomena of
organic life are continually becoming slower. The number of pulsations,
the duration of digestion, the longer continuance of the urine, &c. are
the thermometer of this slowness.

In old age the whole is weakened; the action of the organic muscles
gradually diminishes. Those of the bladder and rectum are the most
exposed to lose their contractile faculty; hence the retention of
urine, which is a frequent companion of old age; hence also the
accumulation of fecal matters above the anus, a disease almost as
common as the first at this age of life, though it has received less
attention from practitioners. Rich people and those accustomed to the
luxury of the table are especially subject to it. I have seen much of
it, as much even as of retention of urine, in the last year of the
practice of Desault. The intestines and the stomach languish more
slowly in their functions. It is the heart which resists the most;
it is the ultimum moriens, as it has been the first in exercise; the
duration of its pulsations measures exactly the duration of organic
life.


_Third Variety. Temperament._

Temperament modifies in a remarkable manner organic contractility. We
know that in some the pulsations are more frequent, the digestive and
urinary phenomena more rapid; that in others, every thing is marked by
more slowness in organic life; now these varieties have evidently their
primitive source in the varieties of the contractility of the heart,
the stomach, the intestines, &c. which have under this relation a great
influence in the difference of the temperaments. With respect to this
there are two essential observations to be made; 1st. The varieties
of force of the organic muscles do not always coincide with those of
the muscles of animal life. Thus we see an individual with feebly
developed exterior forms, with an evident weakness of the muscles of
the extremities, whilst the activity of digestion, of the urinary
evacuations, &c. announces the greatest energy in the sensible organic
contractility. I would remark with regard to this, that the heart is
more frequently in relation of force with the external muscles than the
stomach, the intestines and the bladder. A full pulse, well developed,
is usually found with an athletic constitution; whilst often this
constitution is united in the same subject to a feeble gastric system,
and especially the force of this gastric system is frequently connected
with external weakness. This fact, which the different temperaments
demonstrate to us in man, is evident in the series of animals. Those
who, like the carnivorous ones, have a very powerful animal muscular
system, have the parietes of the gastric cavities like membranes.
These parietes are strong in the herbivorous classes; they become very
conspicuous in the gallinaceous. In general, mastication over which the
animal contractility always presides, is in animals in an inverse ratio
of the force of trituration of the stomach, over which the sensible
organic contractility presides.

2d. The varieties of this property, relative to temperaments, exhibit
another phenomenon almost always foreign to the animal muscular
system. In fact in this the varieties are always general; we are
able by exercise to strengthen this or that muscular region; but the
differences of forces which are natural, always influence the whole
system. The arms and the legs, the thorax and the abdomen are uniformly
contractile in the different divisions of the muscles that belong
to them. On the contrary, it is rare to see this uniformity in the
involuntary muscles. One almost always predominates over the others;
sometimes it is the heart, sometimes the stomach and sometimes the
bladder. The gastric viscera even are frequently not all at the same
level as to force. The stomach is feeble when the intestines preserve
their ordinary action; and reciprocally the intestines too contractile
expel immediately fecal matters and thus produce a diarrhœa, though
the stomach may perform its functions well. This essential difference
in the two muscular systems arises from the circumstance that the
contractility of one depends upon a common centre, the brain; whilst
that of the other on the contrary has its principle insulated in each
organ in which it exists.


_Fourth Variety. Sex._

Women in general resemble children in the phenomena of sensible organic
contractility. The weakness of the motions coincides with their greater
rapidity in this sex, all whose internal muscles, like the external,
are more delicate and less strongly developed than in man. It might
be said that the contractile power of the womb has been formed at the
expense of the forces of all the other organs. In experiments, females
give results much less decided and always less durable than males. The
motions of the heart, the stomach, the intestines, &c. cease sooner;
these motions are less; it requires stronger stimuli to produce them,
&c.


_Fifth Variety. Season and Climate._

In winter and in cold climates, in which the cutaneous organ
contracted, and having as it were the horny hardness from the
impression of the surrounding air, has but a feeble action, all the
internal functions more active, require more energy in the forces that
preside over them; all the digestive, urinary and circulatory phenomena
are more evident. I do not know that there has yet been made any
comparative experiments upon irritability in the different seasons; but
I am persuaded that they would give different results.


_Sensible Organic Contractility considered in relation to the Action of
Stimuli upon the Organs._

We have just described separately the stimulant and the organ
stimulated; each being separate there is no effect upon the sensible
organic contractility; from their union alone results the exercise of
this property. What happens in this union? We know not. To wish to know
it, would be to wish to know how one body attracts another, how an acid
combines with an alkali, &c. In attraction, affinity and irritability,
we can only trace the phenomena to the action of bodies upon each
other. This action is the utmost limit of our researches.

But that which ought not to escape us here is, that in this last
property, the action is never immediate. There is always between
the stimulus and the organ something intermediate which receives
the irritation; this intermediate organ is a delicate membrane and
continuous with that of the arteries for the heart; it is a mucous
surface for the gastric viscera and the bladder. This intermediate
organ is more susceptible of receiving excitement than the muscle
itself. I have uniformly observed that by irritating the internal
surface of the heart, its contractions are greater, than by laying its
texture bare externally by removing its serous covering and afterwards
stimulating it. The same is true with regard to the organic muscles of
the abdomen.

Is there between the intermediate organ excited and the organ which
contracts, any nervous communications that transmit the impression?
I think not, the cellular texture is sufficient. In fact the serous
surfaces and the organic muscles have only this texture as a means
of union. The life of the first is in no way connected with that of
the others, since they often leave them as we shall see, and yet they
can transmit excitement to them. The pericardium and the peritoneum,
irritated in their portion corresponding with the organ that we wish
to move, produce a contraction in it. This fact is known to all those
who have made the least experiment; it is almost always in this way
that we stimulate the heart, the stomach, the intestines, the bladder,
&c. By carrying the stimulus over the serous surface but very lightly,
and so as not to communicate the motion to the fleshy fibres, we
obtain a result. Yet simple contact is not sufficient to transmit
the irritation; for example, by leaving the external layer of the
pericardium applied to the heart and afterwards irritating it, the
organ remains immoveable. If we separate the peritoneum from above the
bladder, so as to break all the cellular adhesions, and afterwards
reapply and stimulate it, the same immobility is observed.

When the intermediate organ that receives the excitement is diseased,
the contractility is uniformly altered. The same stimulus produces slow
or rapid contractions, according as the affection raises or diminishes
the sensibility of this intermediate organ. A slight inflammation of
the exterior of the bladder produces a kind of incontinence of urine;
that of the intestines occasions diarrhœa, &c. &c. On the contrary,
old catarrhs of the bladder, the affections in which weakness of the
mucous surface of this organ predominates, are the frequent causes of
retention.

I would observe that the existence of this intermediate organ is a
remarkable difference between the sensible organic contractility and
the insensible, for this organ does not exist in this last, in which
the same system receives the impression and reacts upon the body that
has produced it; for example, in the glandular, serous, cutaneous
systems, &c. the fluid which enters them for secretion or exhalation
produces in them the sensation, which is instantly followed by the
reaction. In the sensible contractility on the contrary, one system
feels and another is moved. This kind of mobility is less removed from
that of animal life, in which the organs of the senses and those of the
motion being wholly different, are very distant from each other.


_Sensible Organic Contractility considered in relation to its duration
after Death._

This duration is longer than that of the animal contractility. When the
spinal marrow is irritated, the external muscles remain immoveable,
whilst the internal ones are still in activity. There have been so many
examples related of this duration, Haller has multiplied experiments so
much upon this point, that there is no occasion for me to give proofs
here of a fact of which no one can any longer doubt. To this duration
are owing the evacuations of fecal matter and urine which often take
place an instant after death; the vomitings that are observed in some
subjects, if not in as evident a manner as during life, at least
sufficient to raise the aliments into the mouth of the dead body, which
is often completely filled with them, as I have frequently seen.

It is necessary, in relation to this duration, as in relation to that
of the animal contractility, to distinguish two species of death; 1st,
those that take place suddenly; 2d, those which are the consequence of
long disease.

In every sudden death, produced either by a violent lesion of the
brain, as in apoplexy, concussion, compression, effusion, &c. or by
an affection of the heart, as in syncope, a wound, or a ruptured
aneurism; or by a cessation of the action of the lungs, as in asphyxia
from deleterious gases, a vacuum, submersion, &c. the duration of
contractility is very evident; general death comes on first, then the
organs die partially; each vital force is afterwards successively
extinguished.

In every kind of death slowly produced, in all those especially which
are preceded by a disease of weakness, it is the partial death of
each organ that first takes place; each vital force is weakened and
extinguished, gradually, before the cessation of them as a whole, which
constitutes general death, comes on; when this death takes place, none
of the lives peculiar to each organ remains, whilst most of these lives
continue for a longer or shorter time after sudden death.

We cannot make these experiments upon dead bodies which we rarely have
in the hospitals till fifteen hours or more after death; but by killing
dogs by hunger, which, when long continued, becomes a real disease
that lasts in these animals eight, ten and even twelve days, I have
seen the contractility entirely extinguished at the moment of death.
Dogs have been often brought to me affected with different diseases,
especially three years since when there was a kind of epidemic among
these animals; now by opening them at the instant of death, by killing
them even some time before and thus producing a sudden death wholly
different from that which happens in the sound state in which all the
parts are uninjured in their functions and consequently in their vital
forces, I have always seen a constant absence of contractility, or at
least so greatly weakened that it appeared to be nothing.

Many physiologists have spoken of a general convulsion which comes
on in the organic muscles at the instant of death, of a rising of
the heart, the stomach, the intestines, &c. This excess of action is
sometimes real in sudden deaths, in those especially that we produce
for our experiments; it is very rare in deaths preceded by a long
disease in which the patient is extinguished, as it were, insensibly,
and passes gradually from life to death. It is a fault common to almost
all authors, to generalize too much the facts observed under certain
circumstances. Many false consequences are the results of it.


_Sympathies._

No organ receives more easily the influence of others, than the organic
muscles; all however are not equally susceptible of it. The heart
occupies the first rank in this respect; then comes the stomach, then
the intestines, and finally the bladder. It is in this order that we
shall now examine this influence.

It is a remarkable phenomenon, that every kind of affection in any
degree strong, arising in the economy, alters immediately the motions
of the heart. The least wound, oftentimes the slightest pain are
sufficient to produce derangements in it; now these derangements are
of two kinds; sometimes its action is arrested for a moment; hence
syncopes, a mode of derangement which happens especially in violent
and sudden pains. The vulgar expression which is employed in these
cases, viz. "my heart is failing," is perfectly true. Sometimes, and
this is the most common case, this action is accelerated; hence the
febrile motions so frequent in all the local affections, motions purely
sympathetic and which cease when the affection disappears. In many
local inflammations, the evil is too circumscribed to admit an obstacle
to the course of the blood, an obstacle, which according to Boerhaave,
forces the heart to redouble its action to surmount it; besides when
there is no swelling, but only pain in the part, and the febrile motion
comes on, it is there clearly a sympathetic phenomenon. The increase of
the action of the heart may depend no doubt upon a foreign substance,
which, mixed with the blood, alters and renders it more irritating;
it may be owing to an affection of the substance of the organ which
disposes it to be more irritable; but it is certainly very often
sympathetic, and depends upon that unknown relation which connects all
our organs, upon that consensus which links together all their actions,
and places them in reciprocal dependance.

I shall say as much of the stomach; though its sympathetic reaction may
not be altogether as frequent as that of the heart, yet it becomes very
evident under many circumstances. Most local affections, especially
inflammations are accompanied with sympathetic vomitings. Various
fevers have in their commencement similar vomitings. It is in the
hospitals especially that we frequently observe these phenomena. Many
physicians have not considered these vomitings as merely sympathetic,
but as the index of a bilious affection, founded on this, that bile
is then almost always thrown up. But in all the animals that I have
opened, I have almost always seen the stomach when empty containing a
certain quantity of this fluid which had flowed back from the duodenum;
other authors have also made similar observations; so that it appears
that in the state of vacuity, the existence of bile in the stomach
is a natural phenomenon. Hence it is not astonishing, that in the
commencement of diseases, and even in their course, the stomach being
sympathetically excited and thus becoming the seat of vomiting, more or
less of this fluid should be thrown up. It would be brought up even in
health if vomiting is then excited by an emetic; this is what sometimes
happens in the morning when the stomach is empty, if any cause foreign
to an affection of the liver, as the sight of a disgusting object,
produces vomiting; the bile then comes out like every thing else that
is contained in the stomach. I do not say that oftentimes the liver
being sympathetically excited in the commencement of diseases, does
not furnish more bile, that this superabundant bile flowing into the
stomach, does not make this viscus contract; but certainly this is
not most commonly the case; we vomit bile as we discharge it by the
anus, because it is found in the stomach and intestines, and not
because it is superabundant. If vomiting was a natural function, the
bilious evacuations in this way would be as natural as the greenish
tinge of the excrements, which is always found in a state of health.
We see then, from this, that the bilious vomitings are, in many cases,
purely accessory, and that the essential phenomenon is the sympathetic
contraction of the stomach.

In the case of which I have just spoken there is no gastric difficulty;
the sympathetic alteration of the stomach only extends to the fleshy
fibres. But most frequently this gastric difficulty appears at the
beginning of diseases in which there is local affection; sand-like
substances are vomited up; it is because then the organ essentially
affected, the lungs for example, if it is in a peripneumony, has acted
sympathetically not only on the fleshy fibres, but also upon the mucous
membrane. This excited increases its secretion; hence these sand-like
substances, which are nothing but the mucous juices mixed with the
gastric fluid and with the bile; now the presence of these substances
is often sufficient to make the stomach contract, and produce vomiting
which expels them.

From this it is evident that there can be sympathetic vomitings without
gastric difficulty, and sympathetic gastric difficulty with a vomiting
immediately produced. In the first case the fleshy fibres feel the
sympathetic influence of the affected organ; in the second it is the
mucous membrane. But how, when the lungs, the pleura, the skin,
&c. being affected, does the stomach come into action? I have said
that the word sympathy was only a veil for our ignorance in respect
to the relations of the organs to each other. Vomitings produced by
erysipelas, phlegmon, pleurisy, peripneumony, &c. are then most often
an effect exactly analogous to the increase of the action of the heart,
which produces fever. They resemble the cerebral derangement from
which arises delirium, a derangement which is much more rare, &c. All
these phenomena indicate that the other organs feel by reaction the
state of that which is affected, &c. Physicians who have not viewed
all these phenomena in a great and general manner, have confined their
treatment to too narrow bounds. Much attention was formerly paid to the
sympathetic derangement of the heart, and bleeding was much practised
in the beginning of diseases; for some years past much regard has been
had to the sympathetic derangement of the stomach, and emetics are
frequently given; perhaps before long, more attention will be given to
the weights of the head, pains in that part, watchfulness, drowsiness,
&c. which are very common sympathetic symptoms, and the treatment will
be directed to the brain. In these varieties judicious physicians
will regard all these phenomena in a general manner; they will see in
all a proof of that general agreement which disposes together all the
functions, which connects all and thus connects their derangements;
they will see each organ rise up, as it were against the evil which
is introduced into the economy, and each react in its own way; they
will see these reactions producing effects wholly different, according
to the organ reacting, fever arising from the reaction of the heart,
delirium, drowsiness, watchfulness, convulsions, &c. from that of
the brain, vomiting from that of the stomach, diarrhœa from that of
the intestines, gastric and intestinal derangements, foulness of the
tongue from those of the mucous membranes, overflowings of bile from
that of the liver, &c. Thus in a machine in which the whole is united
and connected together, if one part is deranged all the others are so
also. We should laugh at the mechanist who attempted to mend but one
of these pieces, and neglected to repair the local derangement from
which all those arose which the machine exhibits. Let us not laugh at
the physician who attacks only a single symptom, without combating
the disease, of which he oftentimes knows not the principle, though
he knows that this principle exists; but let us laugh at him, if he
attaches to his treatment an importance which is nothing compared with
that of the disease.

The intestines next to the stomach are the most often sympathetically
affected in diseases. The bladder is the organic muscle that is the
last to feel the influences that go from the diseased organ; this
sometimes however happens. In fevers, we know that retentions of
urine from sympathetic and temporary paralysis, are not very rare;
incontinence of urine is less often seen.


_Character of the Vital Properties._

We see from what has been said, that the vital properties are very
active in the organic muscles, especially as it respects contractility.
These muscles are really during life, in constant action: they receive
with great ease the influence of other organs. Their vital properties
are altered with the greatest promptness, especially that which I have
just pointed out; for the insensible contractility is rarely altered in
them, because it does not perform an essential part. Observe in fact
that the morbid derangements of an organ affect always the predominant
vital force of that organ. Animal contractility is frequently
altered in the preceding system; in this it is the sensible organic
contractility. On the contrary, the insensible being very small,
the phenomena over which it presides remain always nearly the same;
nutrition is always uniform; lesions of the muscular texture are rare;
when they take place, it is rather by communication, as in cancers of
the stomach, in which the disease begins upon the mucous surface, and
in which the fleshy fibres are only consequently affected. The heart
and the womb are the muscles that are the most subject to these morbid
alterations; yet in the first they belong oftener to the internal
membrane than to the fleshy fibres themselves. On the contrary in the
systems in which the sensible organic contractility is incessantly in
action, as in the cutaneous, the serous, &c. in which it presides over
nutrition and exhalation; in the glandular, the mucous, &c. in which
it produces secretion and nutrition, it is this which is especially
altered. From these derangements arise alterations of texture, organic
diseases properly called, which are as common in these systems, as they
are rare in those in which the insensible contractility, is so very
obscure, as to be only at the degree necessary for nutrition.

It is to this that must be referred the infrequency of acute
inflammations of this system. As this affection is frequent in the
cutaneous, the serous, the mucous systems, &c. so this system, whose
functions require but little insensible organic contractility, presents
it rarely. Those who open many dead bodies know, that the texture of
the heart is hardly ever found inflamed. Nothing is more common than
phlegmasia of the external or serous membrane, and of the internal
or mucous membrane of the stomach, the intestines, &c. but nothing
is more obscure and less frequently seen than that of their fleshy
tunic. In rheumatism, there is sometimes when the pains cease around
the joints, violent cholics, spasmodic vomitings even, indices perhaps
of an acute affection of the fibres of the stomach or intestines; but
we never find marks of these affections; we do not see the muscular
texture exhibiting the bright red of the inflamed mucous, cutaneous
and serous organs; or at least I have never observed it.

Physicians have not paid sufficient attention to the difference of
inflammations according to the difference of systems; but especially
they have not sufficiently observed that this difference accords
perfectly with that of the insensible organic contractility; that
where this vital force is most characterized, inflammations have the
greatest tendency to take place, because it is this which presides
over their formation; because these affections suppose its increase;
as convulsions suppose the increase of animal contractility, as
vomitings, accelerated pulsations of the heart, suppose that of organic
contractility, &c. I cannot repeat it too much, that the most frequent
diseases in each system, put always in action, raise or diminish the
predominant vital force in that system. It is a new pathological view,
that may be fruitful in results.


ARTICLE FOURTH.

PHENOMENA OF THE ACTION OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

These phenomena are, as in the preceding system, relative to the state
of contraction or to that of relaxation.


I. _Force of the Contractions._

It is never capable of being raised to the point which the force of
the muscles of animal life sometimes attains. Between the strongest
and the weakest pulse, between the feeble jet which precedes some
retentions of urine, and the jet of the most vigorous man, there is
much less difference than between the langour of the voluntary muscles
of some women and the power of those of a maniac, or a man in anger.
The heart and the deltoid muscle are nearly equal in respect to their
fleshy mass; now what would become of the circulation, if the first
sometimes sent the blood with the force which the second uses to raise
the superior extremity? A fit of anger, mania, &c. is sufficient to
produce aneurisms. On the other hand the organic muscles are not
affected with those prostrations of forces so common in the others;
paralysis is foreign to them, because they are not within the cerebral
influence. There is something which answers to convulsions; it is the
irregular agitations which produce so many varieties in the pulse
of acute fevers, agitations which must be distinguished from those
produced by an organic defect of the heart; but these agitations are
wholly different from spasms of the voluntary muscles; there is even no
analogy.

There is not in the force of the contraction of the muscles of which
we are treating, the waste which is so remarkable in that of the other
muscles; the effort is nearly proportionable to the acting cause, and
the distinction of this force into absolute and effective, cannot be
applied here; only there is required more or less contractile energy,
according as the body to be expelled from a hollow muscle, is solid or
fluid. Hence why the great intestines are provided with longitudinal
fibres more characterized than those of the small intestines; why the
rectum especially, in which the excrements have their greatest degree
of solidity, exhibits these fibres in a more evident manner than the
colon or the cæcum, though under a different form; why in diarrhœas the
weakest contraction is sufficient to evacuate the intestines, whilst
the sensible organic contractility of the rectum being insufficient to
void very solid excrements, it is necessary that the abdominal muscle
should aid the expulsion; why when a hard body is introduced into the
stomach, and the gastric juices do not soften it, it remains there a
long time before being expelled, and produces an inconvenient weight,
&c. &c. We know with what rapidity the passage of liquids takes place
from the stomach to the intestines, and how long on the contrary solid
aliments remain in the first.

The force of the organic muscles is incomparably greater in the
phenomena of life than in our experiments. Once laid bare, the heart
communicates only feeble motions, and most often irregular ones. There
is no proportion between the force necessary to produce the jet,
sometimes from seven to eight feet, which the blood exhibits coming
from the open carotid of a dog, and the force of the contractions which
the strongest stimuli produce when applied to the heart extracted from
the body. Nothing equals in our experiments the force of contraction
necessary for vomiting, &c. &c.

Numerous calculations have been made upon the force of contraction,
in the organic muscles as in the preceding, and there has been the
same variety of results. Can we in fact calculate the degrees of a
phenomenon which a thousand causes make vary every instant, not only in
different individuals, but even in the same, which sleep, digestion,
exercise, rest, tranquillity of mind, violence of the passions, day,
night, every thing in a word, incessantly modifies? I do not know that
we digest twice in exactly the same period, if the urine twice remains
the same length of time in the bladder before being discharged, if its
jet is twice exactly equal, &c.

The force of the organic muscles often remains in its ordinary degree,
or is even increased; whilst a general weakness possesses the others.
The force of the pulse, vomiting, diarrhœa, &c. coinciding with a
general prostration of the muscles of animal life, are not rare
phenomena in diseases.


II. _Quickness of the Contractions._

It varies singularly; very rapid in experiments, when death is recent
and the stimuli are very strong, the contractions are in general slower
in the natural state; we might say that it is in the inverse ratio of
the force; often at the instant we open the pericardium, the heart
moves with a rapidity which the eye can hardly follow, especially if we
inject an irritating fluid into this serous sac, a little before laying
the organ bare. The contractions increase much in quickness in certain
diseases; those of the heart, for example, then acquire in the adult
a rapidity often much greater than they have in the first age; this
rapidity is also in this case entirely distinct from the force of its
contractions; it is rare even that these two things are found united at
the highest point. In general when the force of the heart is increased,
there is a little more quickness; but there is very often a diminution
of force with an increase of quickness, or the force remains the same,
the quickness being much increased.

We have seen that the voluntary muscles have in general a degree of
quickness beyond which they cannot go, and that this quickness belongs
to the original constitution. Is not the same phenomenon observed
here? Often in two fevers whose symptoms are the same, whose degree of
intensity seems to be exactly uniform, the pulse is infinitely more
frequent in one individual than in the other. This does not always
denote a difference in the disease, but in the primitive constitution,
an aptitude of one of the two hearts to contract much quicker under the
same stimulant. Who does not know that in experiments, the contractile
rapidity is infinitely variable under the influence of the same causes?

Each organic muscle has its degree of quickness; the heart, the
stomach, the intestines, the bladder, &c. differ remarkably in this
respect.


III. _Duration of the Contractions._

The heart never remains in permanent contraction, as often happens in
the voluntary muscles. Though hunger seems to prove the contrary in the
stomach and the intestines, yet this phenomenon is not contradictory;
in fact, the permanent contraction of the empty gastric viscera is
the result of the contractility of texture. Whenever the sensible
organic contractility is in action, there is alternate contraction and
dilatation; this alternation even characterizes essentially this last
property, and distinguishes it from the animal contractility and from
that of texture, in which the state of contraction is often permanent.


IV. _State of the Muscle in Contraction._

All the phenomena described for the voluntary muscles, are almost
applicable to these, such as the hardening, increase in thickness,
diminution in length, expression of the blood, &c. &c. But there
are some differences between the heart and the gastric muscles, in
respect to the mode of contraction. In fact we see very sensibly in
the first, 1st, contractions of the whole analogous to those of the
voluntary muscles, contractions which take place in the state of
health, which produce the projection of the blood, and which are easily
made in experiments when the animals are still living; 2d, numerous
oscillations which seize upon the fibres, which agitate the whole of
them without producing any sensible effect, without contracting the
cavity, without projecting the blood for example. These oscillations
are observed at the instant of death, when the heart is ceasing to
be contractile; we may then irritate it in vain, there are no more
contractions of it as a whole; though there is a general and very
evident vibration of its fibres, yet its cavity is not contracted; the
blood stagnates in it. The heart perfectly resembles under this double
relation the voluntary muscles; it is agitated as we see these muscles
in the shuddering, that is called horripilatio, as we see it also in
certain sub-cutaneous muscles in some individuals. I have already, for
example, seen many persons affected with an habitual trembling of a
portion of the solæus, a trembling very evident to the eye through the
skin, and which had nothing in common with the contraction necessary to
the extension of the foot.

The involuntary muscles of the abdomen never exhibit this double mode
of contraction. Instead of the quick and sudden motions of the whole
of the muscle, we see but a slow contraction in it, often but slightly
apparent; it is a kind of creeping; there is not even to speak properly
a contraction of the whole, like that of the heart in which all the
fibres of an auricle or ventricle are moved at the same time; here each
fleshy surface appears to act successively. Placed at the origin of
the great vessels, the bladder and the stomach would be incapable of
communicating to the blood those motions by jerks, which the jet of an
artery exhibits at each contraction. On the other hand, at the instant
the motion ends in the stomach, the intestines and the bladder, we
never see in them those oscillations, those vibrations which are almost
constant in the heart and the voluntary muscles, and which we can even
create in them at will.


V. _Motions imparted by the Organic Muscles._

There are hardly ever simple motions in these muscles; the different
interlacing of their fleshy surface allows them to act almost always in
three or four different directions upon the substances they contain.
We can say nothing general upon those motions which compose the
diastole of the heart, the peristaltic motion of the alimentary canal,
the contraction of the bladder, &c. Each muscle has its mechanism
which belongs to the physiological history of the function to which it
contributes.


VI. _Phenomena of the Relaxation of the Organic Muscles._

In the relaxation of the organic muscles, phenomena in general take
place that are opposite to the preceding. It is then useless to
enumerate them; but there is a question here that should be examined,
that of knowing the nature of that state which succeeds contraction and
alternates with it.

In the muscles of animal life, when the contraction ceases, the muscle
does not in general go back itself to the state it was in antecedent
to the contraction, but it is drawn back to it by its antagonist; for
example, when the biceps is contracted to bend the fore-arm and its
contraction ceases, it becomes passive; the triceps putting itself
then in motion, extends it and draws it back to its natural position,
by acting at first on the bones which communicate the motion to this
muscle. Each muscular power of animal life finds then in that which
is opposed to it a cause of return to the state it had left in order
to contract. It is not so in organic life; its muscles, which are all
hollow, have no antagonists. We have considered as such to a certain
extent, the substances contained in the hollow muscles, substances
which oppose the effect of contraction; but incapable most commonly
of reacting after having been compressed, on account of their want of
elasticity, these substances cannot perform the same offices as real
antagonists.

Most physiologists have admitted as a cause of dilatation, the entrance
of new substances, which replace, in the muscular cavities, those
expelled by contraction; thus the entrance of new blood into the
heart, aliments into the different portions of the alimentary canal,
has been considered as proper to dilate these organs; so that according
to this opinion the muscles would be purely passive when they enlarged.
But the following considerations, many of which some authors, Grimaud
in particular, have already stated, do not permit us to consider in
this way the dilatation of the organic muscles, that of the heart in
particular.

1st. When we lay bare a hollow muscle, the heart, the stomach, or the
intestines, and empty it entirely of the substances that it contains,
it contracts and dilates alternately as when it is full, if we apply an
external stimulant to it. 2d. If we empty by punctures all the great
vessels which go to the heart, or come from it, so as to evacuate it
entirely, its alternate dilatations and contractions continue for some
time. 3d. In order to judge comparatively of the degree of force of the
contraction and the dilatation, we can extract two hearts nearly equal
in size from two living animals; place immediately the fingers of one
hand into the auricles or the ventricles of the first, and grasp with
the other hand the exterior of the second; you will feel that one makes
as great an effort in dilating as the other does in contracting. This
fact already observed by Pechlin, is so much the more remarkable, as
the effort of dilatation is often greater than that of contraction. I
have even observed, in repeating this experiment, that whatever effort
we make with the hand, we cannot prevent the organ from dilating.
4th. The alternate extension and contraction, from which arises the
vermicular motion of the intestines, is seen during hunger when we open
the abdomen of an animal. 5th. The hardness of the organic muscular
texture is as evident during dilatation as during vacuity. 6th. I
have many times observed that at the instant in which I irritated the
heart with the point of a scalpel, that a dilatation was the first
consequence of it, and that contraction was only consequent to it.
It happens in general more often that contraction begins the motions
in our experiments; but certainly, the muscle being at rest, it is
frequently a dilatation that first manifests itself.

It appears then very probable that the dilatation of the organic
muscles is a phenomenon as vital as their contraction; that these two
states are united in a necessary manner; that both of them compose
muscular motion, of which contraction is but one part. Who knows even
if each may not be disturbed separately, if to a regular contraction
may not succeed an irregular dilatation and vice versa? Who knows
if certain alterations in the pulse do not belong to injuries of
dilatation and others to those of contraction? I am far from being
certain; for in medicine we must rest our belief on certainty and not
on presumption; but we can make this point an object of research.

It appears that sometimes the voluntary muscles are also the seat of
a true active dilatation. 1st. A muscle, laid bare and extracted from
the body, contracts and afterwards dilates, without being drawn to this
state of dilatation by any cause. 2d. In an amputation, we often see
in the stump the end of the divided fibres alternately lengthen and
contract; a double motion both of which appears to be equally vital.
3d. In many kinds of convulsions in which the extremities stiffen, in
those, for example, which accompany most hysterical fits, it appears
that there is a very evident active dilatation; by placing in fact
the hand upon the muscles which should then be relaxed, from the
disposition of the parts, we perceive a hardness as great as in feeling
of the contracted muscles.

There are many researches to be made upon this mode of dilatation of
our parts, a mode which undoubtedly is not exclusively confined to
the muscular system, but which appears to belong also to the iris, to
the spongy texture of the corpora cavernosa, to the nipples, &c. All
these organs move by dilating very evidently; contraction succeeds in
them expansion, as in the common muscles relaxation does contraction.
Expansion is the principal phenomenon. Perhaps also, as some modern
authors have thought, the sudden swellings of the cellular texture,
which accompany contusions, bruises, &c. are the result of this mode of
motion.


ARTICLE FIFTH.

DEVELOPMENT OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

The organic muscular system is wholly the reverse of the preceding,
as it respects development. This is but slightly characterized in the
early ages, whereas the growth of the other is precocious. Let us
follow it in all the ages.


I. _State of the Organic Muscular System in the Fœtus._

In the first days after conception, the heart is formed; it is the
first point of motion, a punctum saliens, as it has been called. The
researches of different authors, of Haller in particular, have rendered
clear the successive progress of its increase in the early periods.
Rather late in their formation, the muscles of the interior of the
abdomen are yet developed before those that form the parietes of this
cavity. It is the size of the intestines, the stomach, the bladder, &c.
almost as much as that of the liver, which gives to the cavity in which
these viscera are found, the remarkable capacity that it then exhibits.

Nearly uniform at this age, as it respects the proportion of their
size, all the organic muscles are not as much so in regard to that of
their texture. The heart is evidently firmer and more dense than all
the others; its texture is very distinct. The fibres of the stomach,
intestines and bladder are soft and loose and resemble exactly those of
the muscles of animal life; but little blood goes to them in proportion
to what they are afterwards to receive. The fibres of the heart, on
the contrary, dense and compact, have a power of action in proportion
to what they are afterwards to have. Their redness is as distinct; as
much blood penetrates and consequently nourishes them. This redness of
the heart, analogous in the adult to that of the voluntary muscles,
forms at this period a contrast with the remarkable paleness of these
muscles. Besides it has, as in all the other parts where it exists, a
deep tinge, owing to the kind of blood that produces it.

We easily see the reason of the quantity of blood that penetrates the
heart, as this organ then very active in its motions, has need of much
force, whilst the others, almost immoveable, require but little.

Yet the sensible organic contractility of the heart in the fœtus and
in the first age has been exaggerated, undoubtedly on account of the
extreme rapidity that the circulation then exhibits. This rapidity
depends as much on the activity of the tonic forces of the general
capillary system, as on that of the heart; for the blood, when it has
arrived in the capillary system, is wholly beyond the influence of
the heart, as we have seen; the stay that it makes there is wholly
dependant upon the forces of the system itself; now these forces, at
that time very active, accelerate the course of the blood, and send
it into the venous system, from which it goes to the heart. If the
excitability of this were double and even treble, and the blood entered
it but slowly, it would be unable to support a rapid and at the same
time continuous pulse. Haller was drawn to this opinion by believing
that the heart was the only agent of impulse of the blood circulating
even in the small vessels. Besides, there is no doubt that the sensible
organic contractility of the heart is less easily put into action by
experiments in the fœtus, and that it is also much less durable. Then
the strongest stimuli have less effect upon it an instant after death,
than those of less power exhibit upon the heart of an animal that has
been born. I have many times established this fact upon fœtuses of
guinea-pigs. Compared with that of the voluntary muscles, the mobility
of the heart is undoubtedly remarkable in the fœtus; but compared to
what it will be after birth, it is but slight.

It is precisely the same with the contractility of the stomach, the
bladder and the intestines; most commonly we can produce no motion in
these muscles by stimuli. Mr. Léveillé has already made these important
observations; he has also remarked that the urine remained in the
bladder, and the meconium in the great intestines, without producing a
contraction sufficient to expel them. I do not think however that there
could be during life a complete immobility of the gastric viscera,
and for this reason; most commonly the meconium is only met with in
the great intestines; it must have been formed in them then, if there
was complete immobility of the gastric muscles; now it is much more
probable that it is the residuum of the bile, of all the mucous juices,
&c. that consequently it has been pushed successively by a slow action
from the superior part towards the inferior of the alimentary canal.

The softness of the organic muscles renders their extensibility of
texture very great at this period. I would observe however that the
hearts of dead fœtuses do not exhibit those numberless varieties of
size which those of adults do in the right side, according to the
different kinds of death.


II. _State of the Organic Muscular System during Growth._

The first days of existence are marked by an internal motion as quick
in manifesting itself as the external of which we have spoken. The
sucking of the milk, the evacuation of the urine and meconium, &c.
are indices of this general internal motion, of this agitation almost
sudden of all the involuntary muscles.

It is not the brain which, entering into action at birth, produces the
contraction of these muscles, since as we have said they are not under
its government; it appears to depend, 1st, on the sympathetic influence
exerted upon their system, by the cutaneous organ, which is irritated
by the new medium; 2d, on the excitement made upon the beginning of
all the mucous surfaces, and upon the whole of that of the lungs, an
excitement which afterwards reacts upon these muscles; 3d, on that
produced by fluids introduced into the stomach; 4th, on the sudden
entrance of the red blood into all these muscles, till then penetrated
like the others with black; this cause is essential; irritability
appears to be in part dependant on it, or at least to borrow from it a
remarkable increase of force; 5th, the excretion of the meconium and
the urine is also powerfully assisted by the abdominal muscles, which
then enter into activity with the whole system to which they belong.

The general internal motion which takes place in the first moments of
existence, and which is produced by the suddenly increased activity
of the involuntary muscles, has an important use with respect to the
mucous surfaces, which it relieves of the fluids that load them,
and whose presence becomes painful. Where the mucous surfaces have
not around them fleshy layers of the involuntary muscles, as in the
bronchia, the nasal fossæ, &c. the muscles of animal life more or less
distant, perform this function, as for example, the diaphragm and the
intercostals, free the bronchial surface by coughing, and the pituitary
by sneezing.

As we recede from the period of birth, the organic muscles grow in
general much less in proportion than the others; it is this that
gradually re-establishes the equilibrium between the two systems. I
would remark however, as it respects the predominance of the first,
that it is much less conspicuous in the fœtus than that of the nervous
system. The brain, for example, is in proportion much larger than the
heart.

It is probable that the muscles of which we are treating, exhibit, at
this period, the same varieties of composition as the others, that
gelatine especially predominates in them, that they have less fibrin,
&c. This last substance perhaps exists, in the early periods, more
abundantly in the heart than in the other muscles of this class.

We have observed two very distinct periods in the growth of the
other muscles; one is finished when they have acquired their length;
the other, when their thickness is complete. The first has not, in
the organic system, a term as distinct; when the stature no longer
increases, the gastric and urinary organs, and the heart still lengthen
and grow.

We have considered growth in too general a manner. Each system has
a different term in this great phenomenon. The osseous and muscular
systems of animal life, and those which depend on them, as the fibrous,
the cartilaginous, &c. have especially an influence upon the general
stature of the body; it is these which produce this or that height; but
this height has no influence upon the length of the intestines, or the
capacity of the stomach, the heart, the bladder, &c. The glandular,
serous, mucous systems, &c. are equally independent of stature; thus
in these numerous varieties, it has much more influence upon the
extremities, than upon the abdomen, the thorax, &c. A great height
indicates the predominance of the apparatus of locomotion, but not of
those of digestion, respiration, &c. The termination of the growth in
height, which we consider in a general manner for the whole body, is
only the termination of the growth of the muscles, the bones and their
dependancies, and not of that of the internal viscera, which still
lengthen and become thicker. It is easy to be convinced of this, by
comparing the organic muscles of a young man of eighteen years, with
those of a man of thirty or forty.

The organic muscles do not appear to be subject to those irregularities
of growth which the other muscles and the bones frequently exhibit.
We know that the stature often remains stationary for many years,
and that suddenly it acquires very great dimensions in a very short
time; this phenomenon is remarkable especially after long diseases.
Now notwithstanding these inequalities, the heart and all the other
analogous muscles grow in an uniform manner; the regularity of the
internal functions to which these muscles especially contribute, could
not adapt itself to those aberrations which would be unable to disturb
the functions of the locomotive organs. Besides, if they took place,
the circulation, digestion, excretion of urine, &c. would exhibit
corresponding aberrations; now this is never observed. The heart and
the gastric muscles, &c. always grow in an infant whose stature remains
stationary; they do not grow suddenly in one who grows at once; hence
why the thorax and the abdomen become large in the first case, and
remain contracted in the second in proportion to the extremities.

Besides these two systems are never in precise relation of nutrition
and power. I have already observed that very large organic muscles
often exist with very small voluntary ones, and vice versa.

Let us consider neither the growth nor nutrition in an uniform manner;
each system is developed and increases in its own way; all are never
found at the same periods of this function. Why? because nutrition,
like all the other acts over which life presides, is essentially
dependant on the vital forces, and these forces vary in each system.

The growth of the involuntary muscular system is not uniform in all the
organs which compose it. Each increases more or less, or is differently
developed; one often predominates over the others in an evident manner;
a bladder with strong, fleshy fibres, with columns as they are called,
is often found in a subject with a debilitated stomach, with small
intestines, &c. reciprocally, the stomach, the heart, &c. have often
an insulated predominance.


III. _State of the Organic Muscular System after Growth._

It is from the twenty-fourth to the twenty-sixth year, that the organic
muscles are completely developed. Then the thorax and the abdomen which
contain them have their greatest capacity. These muscles are then as
they are to remain through life; they have a density much greater
than in youth; their power is increased and their colour is deeper.
In general this is subject in the heart to frequent varieties, which
coincide very nearly with the varieties of the preceding system. Acute
and chronic diseases have nearly the same influence upon it. It is
equally the index of the sanguineous, lymphatic temperaments, &c. by
the different tinge it assumes. The colour of the gastric, intestinal
and vesical fibres varies less; their whiteness, more uniform, is
rarely influenced by diseases.

We cannot increase, by constant exercise, the nutrition of the organic
muscles. Aliments taken beyond measure, making the stomach frequently
contract, weaken it instead of developing its fibres more, as happens
from constant exercise given to a superior or inferior extremity. The
bladder incessantly in action in some cases of incontinence, is thus
gradually weakened and loses its energy. We might say that these two
systems were in this respect in an inverse order.

It appears that the nutrition of the organic muscles, like that of
the others, is subject to frequent variations; that at some periods
they are more developed and less so at others. Diseases have a great
influence upon this phenomenon, which proves, like the softening of the
bones and their return to the natural state, the constant composition
and decomposition of which these organs are the seat. We find in the
dissecting rooms many differences in different subjects, as it respects
the colour, density and cohesion of the muscles. Now what many exhibit
then at once, the same individual often experiences successively; the
same man no doubt has, according to the different influences to which
he is exposed, his heart red, dense, large and well nourished at one
period of life, and feeble, pale and small at another; for the internal
organs experience the same alterations as the exterior. Now we know
that the external appearance often changes during life.


IV. _State of the Organic Muscular System in Old Age._

As we advance in age, the muscular system of which we are treating
becomes weak like all the others; yet its action is more durable;
it survives, if we may so say, that of the other. When the old
man, almost immoveable, crawls about but slowly and with pain, his
pulse, digestion, &c. have vigour still. This difference of the two
systems is so much the more remarkable, as the time of activity of
the second is almost by half less than that of the first; sleep cuts
off in fact almost half of the duration of the voluntary motions,
whilst it leaves the involuntary wholly untouched. This phenomenon of
the organic muscles as it were surviving the voluntary in the last
periods of life, is derived on a great scale from the same principle
from which arises on a small one the lassitude which follows the
contraction in an insulated motion. A less durable motion is necessary
to fatigue the voluntary muscles, than to fatigue the involuntary; the
stomach empty remains for a long time contracted upon itself without
producing any painful sensation, whilst if we hold a body strongly
grasped between our fingers for a quarter of an hour, all the flexors
are soon painfully affected. After a convulsion of half an hour, in
which all the locomotive muscles have been stiff, the whole body is
broken, as it is called; it cannot admit of any motion; whilst after
a paroxysm of fever of six or eight hours in which the pulse has been
violently agitated, the heart often preserves the natural type of its
contractions; it requires repeated paroxysms to weaken it. All these
phenomena of the two muscular systems evidently prove that that of
animal life is fatigued much the soonest; it is this which occasions
its intermission. Is it then astonishing that, although less often in
exercise than the other, it exhausts sooner the quantum of force nature
has given to it? is it astonishing that the other survives the longest?
Life is a great exercise which gradually wears up the organs in motion,
and which requires their rest; this rest is death; now each moveable
organ arrives at it sooner or later, according to the different degree
of the forces which it has to expend, and according to its greater or
less disposition to be wearied by this great exercise.

Yet the organic muscles are gradually weakened. The pulse becomes
slower, digestion is longer in old age; the bladder and rectum first
cease to act; then the intestines remain inactive; the stomach and
especially the heart die the last.

A long time before death, the muscular cohesion is weakened in this
system as in the preceding; the fleshy texture becomes flaccid; the
parietes of the heart support themselves in youth; they flatten in
old age. The gastric system of a young animal suddenly killed during
hunger is firm, dense and contracted upon itself; in an old one, under
the same circumstance, it is but little contracted; the stomach and
intestines remain much more dilated; they are loose and soft; it is
the same phenomenon as in the preceding muscles, which vacillate under
the skin, from want of cohesion. The bladder remains constantly large,
though empty.




MUCOUS SYSTEM.


This system, the name of which I borrow from the fluid that constantly
lubricates it, and which is furnished by small glands inherent in its
structure, appears everywhere in a membranous form; that of fasciculi
is wholly foreign to it. In speaking of the mucous organs we shall
designate them almost always under the name of membranes. Their study
is a new object of research. Pinel has been among the first, who has
perceived the necessity of considering them in a general manner as
it respects diseases. I believe that I am the first who has regarded
them generally in an anatomical and physiological view. Few systems
deserve more attention; upon it take place all the great phenomena of
digestion, respiration, secretion, excretion, &c. it is the seat of
many diseases. It should alone, in a nosography in which diseases are
distributed by systems, occupy a place equal to that of many.


ARTICLE FIRST.

OF THE DIVISIONS AND FORMS OF THE MUCOUS SYSTEM.

The mucous membranes occupy the interior of the cavities which
communicate with the skin by the different openings this covering
has on the surface of the body. Their number at first view is very
considerable; for the organs in which they are reflected are very
numerous. The mouth, the stomach, the intestines, the œsophagus, the
bladder, the urethra, the womb, the ureters, all the excretories, &c.
&c. derive from these membranes a part of their structure. Yet if
we consider that wherever they are continuous, wherever we see them
originate, by extending from each other, as they originated in the
first instance from the skin, we shall perceive that this number must
be wonderfully limited. In fact by thus describing them, not separately
in each part, but at the same time in all those upon which they are
continued, we see that they are reduced to two general surfaces,
of which all the others are portions, and which, on account of the
different parts to which they are distributed, can be called, the one
gastro-pulmonary, the other genito-urinary. The first is found in the
head, the neck and the abdomen. This last cavity and more especially
the pelvis, contain the second.

There is also a small insulated mucous surface; it is that which enters
by the openings of the nipples and lines the lactiferous tubes. But it
is so small that it deserves but little attention; besides, what will
be said of the two others will be equally applicable to it. It is then
useless to examine it in a general manner.


I. _Of the two General Mucous Membranes, the Gastro-Pulmonary and the
Genito-Urinary._

The gastro-pulmonary surface penetrates into the interior by the mouth,
the nose and the anterior face of the eye. 1st. It lines the first and
second of these cavities, extends from the first to the excretory ducts
of the parotid and sub-maxillary glands, from the other into all the
sinuses, forms the conjunctiva, dips down into the puncta lachrymalia,
the nasal duct, the sac of the same name, and is continued into the
nose; 2d, it descends into the pharynx, furnishes an elongation to
the Eustachian tube, then penetrates the internal ear and lines it, as
we shall see; 3d, it dips down into the trachea and is spread upon all
the air-tubes; 4th, it penetrates into the œsophagus and the stomach;
5th, it extends to the duodenum where it furnishes two elongations,
one destined to the ductus choledochus, to the numerous branches of
the hepatic and cystic ducts and the gall-bladder, the other to the
pancreatic duct and its different branches; 6th, it is continued into
the small and large intestines and finally terminates at the anus where
we see it identified with the skin.

The second general mucous membrane, which we have called the
genito-urinary, enters in man by the urethra, and thence is spread on
the one hand upon the bladder, the ureters, the pelvis of the kidnies,
the infundibula, the papillæ and the capillary tubes which open on
their summit; on the other hand it goes into the excretory tubes of
the prostate, into the seminal ducts, the vesiculæ seminales, the vasa
deferentia and the branches with numberless windings that produce them.

In woman, this membrane is introduced by the os externum and
penetrating on the one hand by the urethra, goes as in man upon the
urinary organs; on the other hand, we see it enter the vagina, lining
it, the uterus and the fallopian tubes, and afterwards becoming
continuous with the peritoneum by the opening of these tubes. It is the
only example in the economy, of a communication established between the
mucous and serous surfaces.

This manner of describing the course of the mucous surfaces, by saying
that they are elongated, dip down, penetrate, &c. from one cavity to
another, is no doubt not conformable to the progress of nature, which
creates in each organ the membranes belonging to this organ, and does
not thus extend them by degrees; but our manner of understanding it
is better adapted to this language, the meaning of which the least
reflection will show.

In thus referring to two general membranes all the mucous surfaces,
I am not only supported by anatomical inspection, but pathological
observation has also furnished me with points of demarcation between
the two, and points of contact between the different portions
of membranes of which each is the assemblage. In the different
descriptions of catarrhal epidemics given by authors, we frequently
see one of these membranes affected in all parts, the other remaining
sound; it is especially not rare to observe a general affection of the
first, of that which extends from the mouth, the nose, the surface of
the eye, into the alimentary canal and the bronchial vessels. The last
epidemic observed at Paris, with which Pinal himself was affected,
was of this character; that of 1761, described by Razou, had it also;
that of 1752, described in the memoirs of the Society of Edinburgh was
remarkable for a similar phenomenon; now, we do not see at that time
a corresponding affection in the mucous membrane that is spread upon
the urinary organs and upon those of generation. There is then here,
1st, an analogy between the portions of the first, by the uniformity of
affection; 2d, a demarcation between the two by the health of the one
and the disease of the other.

We see also that the irritation of any one point of one of these
membranes, frequently produces a pain in another point of the same
membrane, which is not irritated. Thus a calculus in the bladder
occasions a pain at the end of the glans penis, the presence of worms
in the intestines causes an itching of the nose, &c. &c. Now, in
these phenomena purely sympathetic, it is very rare that the partial
irritation of one of these two membranes affects with pain one of
the parts of the other; there are however examples of it; such is
the singular relation that exists, in mucous hemorrhages, between
the membrane of the womb and that of the bronchia. If the blood
ceases accidentally to flow from one during menstruation, the other
frequently exhales it and thus as it were supplies its functions.

We ought then, from inspection and observation, to consider the mucous
surface, in general, as formed by two great membranes successively
spread upon many organs, having between them no communication except
by the skin, which serves them as an intermediate organ, and which,
continuing with both, contributes thus with them to form a general
membrane everywhere, continuous, covering the animal externally, and
extending within upon most of its essential parts. We can conceive
that there should exist important relations between the internal and
external portion of this single membrane; and that they do will be
proved by further researches.


II. _Adhering Surface of the Mucous Membranes._

Every mucous membrane exhibits two surfaces, one adhering to the
neighbouring organs, the other free, covered with villi, always
moistened with a mucous fluid. Each deserves particular attention.

The adhering surface corresponds almost everywhere with the muscles,
either of animal or organic life. The mouth, the pharynx, the whole
alimentary canal, the bladder, the vagina, the womb, a portion of the
urethra, &c. exhibit a muscular layer embracing on the outside their
mucous tunic which is within. This arrangement coincides perfectly, in
animals with a fleshy membrane, with that of the skin, which moreover
approximates very near, as we shall see, the structure of the mucous
membranes, and which, as we have seen, is everywhere continuous with
them. This arrangement of the mucous membranes occasions them to be
agitated by constant motions which favour wonderfully the secretion
that takes place in them, the excretion which succeeds it, and the
various other functions of which they are the seat. The insertion
of this muscular layer exterior to the mucous system, is made, as we
have seen, by this dense and compact texture which I have called the
sub-mucous. It is from this texture, more compact than the rest of the
cellular system, that the mucous surface derives its force. It is from
it that the organ which it lines receives its form; it is this which
supports and preserves this form; the following experiment proves it.
Take a portion of the intestine; remove from any part of it this layer,
as well as the serous and the muscular; then inflate it, after having
tied it below; the air produces in this place a hernia of the mucous
coat. Try afterwards another portion of intestine; deprive this, for a
small space, of its mucous membrane and of this also; inflation will
produce upon the serous and muscular tunics the same phenomenon that
it did in the preceding on the mucous; then it is to this sub-mucous
cellular layer that it owes the resistance with which it opposes
substances that it contains. The same may be said of the stomach, the
bladder, the œsophagus, &c.


III. _Free Surface of the Mucous Membranes._

The free surface of the mucous membranes, that which is continually
moistened by the fluid from which they borrow their name, exhibits
three species of wrinkles or folds.

1st. One inherent in the structure of all the laminæ of these
membranes, is constantly met with, whatever may be their state of
dilatation or contraction; such are those of the pylorus and the valve
of Bauhin. These folds are formed not only by the mucous membrane, but
also by the intermediate tunic of which we have spoken, which here has
a remarkable density and thickness, and gives them solidity. The fleshy
tunic enters even into their composition, and we see on the exterior,
upon the serous surface, a depression that indicates their presence.

2d. Other folds, only formed by the mucous surface, exist also always
in a state of vacuity or fulness, less evident however than this; they
are owing to the circumstance that the mucous surface is much more
extensive than those upon which it is applied, so that it is folded
that it may not run a longer course; such are the valvulæ conniventes
of the small intestines, the structure of which we see very well
by cutting longitudinally one of these intestines. The edge of the
section exhibits the fleshy layer and the serous surface in a straight
direction, whilst the mucous layer describes a line resembling a loose
thread.

3d. The last species of folds is as it were accidental, and is only
observed during the contraction of the organ which is lined by the
mucous surface that is the seat of it; such are those of the interior
of the stomach, the great intestines, &c. In the greatest number of
subjects brought to the dissecting rooms, these folds of which so
much has been said as it respects the stomach, cannot be perceived in
it, because the subject has died after a disease that has so altered
the vital forces, as to prevent all action of this viscus; so that
though it is frequently found empty, its fibres are not contracted.
In experiments upon living animals, on the contrary, these folds
become very evident, and may be demonstrated in this way; make a dog
eat or drink copiously, open him an instant after and cut the stomach
in the length of its great curvature; no fold is then apparent; but
soon the viscus contracts, its edges are turned over and the aliments
escape; the whole mucous surface is covered with an infinite number
of very prominent ridges, which have as it were the form of cerebral
circumvolutions. We obtain the same result by taking out the stomach
of an animal recently killed, distending it with air and opening it
afterwards, or by cutting it immediately in its state of vacuity and
drawing it in opposite directions by its edges; it stretches, its
ridges disappear, and if we cease to distend it, they form again
immediately in an evident manner. I would observe on the subject of the
inflation of the stomach, that by distending it with oxygen, we do not
produce by the contact of this gas, greater ridges and consequently
a stronger contraction, than by using for the same purpose carbonic
acid gas. This experiment furnishes a result very similar to what I
have observed in rendering animals emphysematous by different aeriform
fluids. It follows from all that we have said upon the folds of the
mucous membranes, that in the ordinary contraction of the hollow organs
which these membranes line they undergo but a very slight diminution
of surface, that they contract scarcely at all, but fold within, so
that by dissecting them on an organ in contraction we should have a
surface almost equal in extent to that which they exhibit during its
dilatation. This assertion, which is true as it respects the stomach,
the œsophagus and the great intestines, is not perhaps as entirely so
with regard to the bladder, the contraction of which makes the ridges
within less evident; but they are not sufficient to destroy the general
law. It is also nearly the same with the gall-bladder; yet here we
find another cause. The gall-bladder, alternately observed in hunger
and during digestion, contains double the bile in the first case
that it does in the second, as I have had occasion to see very often
indeed, in experiments made for this object or with other views. Now,
when the bladder is in part empty, it does not contract upon the bile
that remains, with the force of the stomach when it contains but few
aliments, or with the power of the bladder when it contains but little
urine. It is then flaccid; so that its being distended or not has but a
slight influence upon the folds of its mucous membrane.

Besides, in saying that the mucous membranes always exhibit, with some
slight difference, the same surface in the extension and contraction
of their respective organs, I intend to speak only of the ordinary
state of the functions, and not of those enormous dilatations of
which we often see the stomach, the bladder, and more rarely the
intestines become the seat. Then there is no doubt, a real extension
and contraction, which coincide in the membrane with those of the organ.

A remarkable observation which the free surface of the mucous membranes
exhibits, and which I have already pointed out, is, that this surface
is everywhere in contact with bodies heterogenous to that of the
animal, whether these bodies introduced from without to nourish it have
not yet been assimilated to its substance, as we see in the alimentary
canal and in the wind-pipe; or whether they come from within, as we
observe in all the excretory ducts of the glands, which all open into
cavities lined by the mucous membranes, and transmit without particles
which, after having contributed for some time to the composition of
the solids, become heterogeneous to them, and are separated from them
by the constant motion of decomposition which takes place in living
bodies. Hence we ought to regard the mucous membranes as limits, and
barriers, which, placed between our organs and the bodies that are
foreign to them, defend them from the mischievous impression of these
bodies, and serve consequently within, the same functions which the
skin performs without, with respect to the bodies which surround that
of the animal, and which tend incessantly to act upon it.

The organization of the mucous system and its vital properties are
accommodated to this habitual contact of substances heterogeneous to
the living economy. That which is a foreign body to the other systems,
the cellular, the muscular, &c. is not so to this. Solid substances,
the metals, stones, wood, &c. which introduced into our parts excite
in them inevitably suppuration and an antecedent inflammation by
their simple contact, pass with impunity over this, provided that
their angles and asperities do not tear it; they only augment a
little the secretion, as I shall say. We can swallow a ball of lead,
of wood, &c. and pass it by the anus without inconvenience. All the
irritating fluids without being caustic, that we inject into the great
intestines in enemas, or that we swallow, would produce abscesses,
&c. if they were forced into the cellular system, &c. Surgeons employ
the term foreign bodies in too general a manner; that which is so
for one system, is not for another. Foreign is, in this respect, a
term of comparison which we should employ only after a knowledge of
the peculiar sensibility of each system, and not after that of this
property described in a vague manner.

The mucous system not only bears without danger the presence of all
bodies that are introduced into the economy, but also when it goes out,
it can be exposed with impunity to the contact of external stimuli.
Observe what takes place in prolapsus of the womb in which the whole
membrane of the vagina sometimes becomes external, in those inversions
of the intestinal tubes that take place through preternatural ani, in
prolapsus of the rectum, &c. then the mucous surfaces serve really as
integuments; now in these cases the surrounding bodies produce hardly
any more pain on them than upon the skin. On the contrary, the instant
a serous surface is laid bare, as for example in the operation of
hernia, in which the intestine is suffered to come out, on account of
an opening unfortunately made by the point of a bistoury, this surface
inevitably inflames. All the cellular, muscular, nervous, glandular
systems, &c. laid bare, exhibit the same phenomenon. There is no danger
in opening the bladder as it respects the contact of the air, whilst
there is much in permitting this fluid to penetrate into an articular
cavity, a tendinous groove, a serous sac, &c. We know how much in
the high operation for the stone, we fear to wound the peritoneum,
how uncertain are the results of empyema on account of the contact
of the air upon the pleura, &c. The dangers of the action of this
fluid upon these surfaces have been perhaps exaggerated, but they are
notwithstanding real.

If a fistula extends from the exterior of the abdomen into the
intestines, its whole course is lined with callous bodies; these defend
the cellular texture and the muscles through which the fistula passes.
On the contrary, nothing similar appears upon the intestinal mucous
surface, because its organization alone is sufficient to protect it.
The urinary, salivary and lacrymal fluids never escape externally by
artificial ducts formed in the neighbouring organs, without there are
similar callous bodies in the course of these ducts; on the contrary,
they pass with impunity over the mucous surfaces. Make in a limb a
long and straight opening with a pointed instrument, and fix in it for
a time a sound; a callous canal will be produced by it. Let a sound
on the contrary remain in the urethra, no alteration of texture will
result from it.

Let us conclude from these different considerations, that the mucous
system with the cutaneous alone, is organized so as to support the
contact of all external bodies, and not to be affected by their
presence, or at least experience only an increase of secretion, which
is in no ways dangerous. Thus these two systems form two boundaries,
the one internal and the other external, between which are placed the
organs foreign, by their mode of sensibility and by that of their
structure, to the external bodies. To these boundaries the excitement
of these bodies is limited; their influence does not go beyond. So
long as they do not pass these boundaries, the other organs do not
feel them. We might say that the acute sensibility which each of them
enjoys, is a kind of sentinel that nature has placed on the confines of
the organic domain of the mind, to inform it of whatever can injure it.


ARTICLE SECOND.

ORGANIZATION OF THE MUCOUS SYSTEM.


I. _Texture Peculiar to this Organization._

The mucous system presents two things to be considered in its peculiar
texture, viz. 1st, a layer more or less thick which constitutes
principally this texture, and which by analogy with the cutaneous
corion, may be called the mucous corion; 2d, many small elongations
which surmount it, and which are called villi or papillæ. As to the
epidermis which covers it, I shall treat of it with the cutaneous
epidermis. This texture has nothing similar to the substance that
colours the skin, and which is between the papillæ and epidermis. We
know in fact that negroes, as well as whites, have this texture of a
bright red, which it derives from its vessels.


_Mucous Corion._

This portion of the mucous texture, which is the most important, and
which constitutes the thickness, form, and even the nature of it, has
a soft and spongy appearance. We might say at first view that it was a
consistent pulp, with which the extremely dense cellular texture that
is subjacent to it had been covered. This softness is a character which
distinguishes it from the cutaneous corion, which moreover has by its
intimate nature but little resemblance to it.

The mucous corion is very various as to thickness; it differs in
this respect in each organ. That of the gums and the palate is the
thickest of all. Then come those of the nasal fossæ and the stomach,
then those of the small intestines and the gall-bladder, then those
of the large intestines, of the urinary bladder, the urethra and the
other excretories, until it begins at length to become so fine as to
appear transparent like a serous surface when it is removed with care.
Finally, the finest and most delicate is that of the sinuses of the
face and the interior of the ear; the arachnoides is often coarser.

I have called the texture within the ear mucous, though all anatomists
call the membrane of the cavities of this organ periosteum. In fact,
1st, we see it evidently continued with the pituitary membrane,
by means of the elongation of the Eustachian tube. 2d. We find it
constantly moistened by a mucous fluid which this canal serves to
convey out, a character foreign to the periosteum, which, like the
fibrous membranes, always adheres by both its surfaces. 3d. No fibre
can be distinguished in it. 4th. Its fungous appearance, though white
and soft, and the ease with which it is torn, are evident attributes
of the mucous membranes. Every thing proves that the membrane of the
tympanum, that of the meatus, &c. belong to the system of which we are
treating. Thus in catarrhs of the pituitary membrane, and of that of
the fauces, we most often find that the ear is affected; thus the ear
is, like the mucous surfaces, the seat of hemorrhage, thus polypi arise
in it, as in the nose and on the surface of the womb. We consider as a
sign of deposition of pus in the ear, every purulent discharge coming
from that cavity. But how can we conceive of a purulent collection in
a part in which there is hardly any cellular texture, in a part wholly
osseous? Besides the fibrous system, to which the periosteum of the
tympanum belongs, hardly ever suppurates, as we know. Every thing then
induces us to believe that these discharges are only the effect of a
catarrh of the ear, a catarrh which is sometimes acute and sometimes
chronic. I have moreover a recent and decisive fact upon this point;
the body of a man subject to these discharges during life exhibited
a remarkable thickness and redness of the membrane of the tympanum,
but without the least trace of erosion. The ear suppurates like the
urethra, the vagina, &c. it is not a new fluid which is formed by
suppuration; it is that which naturally comes from the meatus which
increases in quantity and comes through a preternatural opening of the
membrane of the tympanum.

Diseases make the thickness of all the mucous surfaces vary remarkably.
I have seen them many lines thick in the maxillary sinus, and nearly
half an inch in the bladder. In great extensions of the mucous
sacs, this thickness diminishes very much; it increases in their
contractions. The stomach especially exhibits this phenomenon in these
two opposite states.

The softness of the mucous corion is also very variable; in the nasal
fossæ, in the stomach and the intestines, it is really a kind of
organized velvet. The name of villous membrane is perfectly suited to
it. On the contrary, at the origins of the mucous system, as in the
mouth, upon the glans penis, at the entrance of the nose, it is a more
dense and compact texture, approximating nearer in its nature to the
cutaneous corion. I am persuaded that like this it might be tanned and
be useful in the arts if it were in larger pieces, whilst I doubt if
the action of tanning could produce an analogous phenomenon upon the
mucous texture of the deep-seated organs. The softness of this would
render it incapable of serving for external integuments. The least
cause would be in fact sufficient to break and tear it. Its structure
being different from that of the cutaneous corion is the reason that
the variolus pustules never appear on it, whilst we often see them on
the mucous surfaces near the openings of the skin, especially upon the
tongue, the palate and the internal surface of the cheeks.

Exposed to the action of dry air, so that it may come everywhere in
contact with it, it becomes dry and very thin, but preserves some
resistance. In bladders inflated and dried, in the stomach, the
intestines, &c. thus prepared, it is this texture which supports these
organs, and which prevents them from becoming flat, though we permit
the air to escape; it offers even a resistance, from which arises a
kind of crepitation when we wish to bend them in various directions. To
be convinced of this, it is only necessary to dry the mucous surface
separate from the serous and muscular that correspond with it; these
when dried remain pliable like the cellular texture, whilst the first
has a kind of rigidity.

In the organs in which the redness of the mucous texture is slight, as
in the bladder, the rectum, &c. it becomes transparent by drying. Where
it is very red as in the stomach, it takes a deep tinge, which becomes
even almost black if there had been an antecedent inflammation in it by
which much blood had been accumulated; hence it appears that this fluid
is the cause of the colour.

Thus dried the mucous surfaces are smooth; they lose their viscidity at
least in appearance; their folds are effaced by adhering to the surface
from which they arise; thus the valvulæ conniventes are marked in a
dried intestine, only by a red line, without any apparent prominence.
But if we macerate the intestines in this state, the folds form again
and become visible.

Exposed to a moist air, or left with other flesh that will not allow
it to become dry, the mucous corion putrefies with great ease; the
odour that it then sends out is very fetid. I think the reason why
the abdomen of dead bodies becomes putrid so soon is in part because
it contains substances already in putrefaction, and also because the
surfaces, in contact with these substances, and which by their vitality
resisted before their action, then readily yield to them. If these
substances were contiguous to aponeuroses, putrefaction would be much
less rapid. The mucous system when putrid takes a greyish colour; and
as the dense, subjacent cellular texture putrefies much less easily,
we can then remove from it by the least pressure, the mucous corion,
reduced to a putrid pulp, in which every trace of organization has
disappeared, and which forms a real pap.

During life, gangrene of the mucous texture takes place in general less
frequently than that of the cutaneous. The consequences of catarrh,
compared with those of erysipelas may convince us of this; there are
however cases in which death appears in this texture, whilst the
surrounding ones continue to live, as in gangrenous angina.

Exposed to maceration, the mucous texture yields to it promptly. I
think that next to the brain it is altered quickest by the action of
water. It is then reduced to a reddish pulp very different from that
from putrefaction in the open air. When we put the whole stomach to
macerate, this pulp is detached, when the sub-mucous texture and the
serous membrane have as yet undergone but little alteration.

Ebullition at first extracts from the mucous texture a greenish scum,
very different from that which the muscular and cellular textures
give when boiled. This scum which mixed with the whole fluid in the
beginning of the boiling, disturbs it and renders it green at first,
afterwards rises upon the surface where it has small bubbles of air
mixed with its substance; it often even falls to the bottom of the
vessel by its weight. Sulphuric acid changes the colour of it to a dull
brown.

A short time before the water begins to boil, the mucous texture
crisps and acquires the horny hardness like the others, but in a
less degree however; hence why it is then wrinkled almost always in
different directions. In fact, the sub-mucous texture upon which it is
applied, contracting at that time much more than it, it must fold on
account of its length; thus during life, when the fleshy coat of the
stomach contracts, its mucous surface not contracting in proportion,
produces the numerous folds of which we have spoken. The action of a
concentrated acid crisping the sub-mucous texture more than the mucous
itself, produces an analogous phenomenon. After having been a long time
dried, the mucous texture, like however almost all those of the animal
economy, does not lose the faculty of acquiring the horny hardness when
it is plunged into boiling water; it exhibits this phenomenon, whether
we expose it to it dry, or whether we do it after having first softened
it in cold water. It is a means by which all the valvulæ conniventes
may be made suddenly to reappear, which had disappeared by drying, and
which form again the instant the intestine contracts. This experiment
is very curious to witness.

When the ebullition has been a long time continued, the mucous texture
turns gradually to a very deep grey, from the white which it had first
become. It is not softer than in the natural state, but it breaks
much quicker; the following experiment is a proof of it. If we draw
the mucous corion, boiled for some time with the subjacent cellular
texture, this last resists the most; so that it remains entire, whilst
the mucous corion is broken in many places. This never assumes the
gelatinous appearance of the cutaneous corion or the fibrous and
cartilaginous organs when boiled and of the others which yield much
gelatine. However by mixing a solution of tannin with the water in
which this system taken from an adult has been boiled, I have seen an
evident precipitate.

The action of the acids reduces to a pulp the mucous texture much
sooner than most of the others. During life, all the caustics act
much more rapidly upon it than upon the cutaneous, of which the
thick epidermis is an intermediate organ which checks their tendency
of combining with its corion. Thus the instant the nitric acid, a
substance which common people almost always choose for their poison, as
the practice at the Hôtel Dieu proves, thus the instant I say, that the
nitric acid is in contact with the alimentary canal, it disorganizes
it, it forms there a whitish eschar, which, when death does not take
place immediately, as most often happens, is slowly removed and
detached in the form of a membrane. We know that the lips gently rubbed
with weakened nitric acid, become the seat of a troublesome itching,
whilst that oftentimes though this acid may have acted upon the skin
sufficiently to make it yellow, it does not suffer from it.

The softness of the mucous corion makes me presume that it is easily
altered by the digestive juices, not that I confide in the experiments
of Hunter, who pretended that these juices could act upon the coat that
secretes them, but because in general I have observed that the textures
like it yield very easily to the action of water in maceration and are
also very easily digested. I have not however any experiment upon the
subject, and we know that in the animal economy analogy is not always a
faithful guide.

All the mucous surfaces, but especially that of the stomach and
intestines, have the property of curdling milk, as have many other
substances, especially the acids. Is it to this property that must
be attributed a phenomenon which is constant during life, viz. the
coagulation of milk that enters the stomach for digestion? or is
this phenomenon owing to the mixture of this fluid with those which
are secreted by the surface of this organ? I think that both these
causes contribute to it at the same time; both separate produce in
fact this phenomenon. Spallanzani has proved it as it respects the
gastric juices. Every body knows that the mucous membrane dried, and
consequently deprived of these juices, preserves the property of
coagulating milk. Spallanzani has convinced himself that the serous
and organic muscular systems of the stomach are destitute of it.

Are aphthæ an affection of the mucous corion? do they belong to
the papillæ? are they seated in the glands? are they a separate
inflammation of these glands, whilst catarrhs are characterized by a
general inflammation of a considerable extent of the mucous system? All
these questions deserve to be examined. Pinel has perceived the void
there is in morbid anatomy upon this point.


_Mucous Papillæ._

The peculiar kind of sensibility which the skin enjoys is attributed
principally, as we know, to what is called the papillary body, which
commonly is not easy to be demonstrated. The sensibility of the mucous
membranes, somewhat analogous to that of the skin, appears to me to
have the same kind of organization, which is perceived with infinitely
less ease. The papillæ of this system cannot be called in question at
its origin, where it dips into the cavities, in the commencement even
of these cavities, as upon the tongue, the palate, the internal part of
the alæ of the nose, upon the glans penis, in the fossa navicularis,
within the lips, &c. Inspection is sufficient to demonstrate them
there. But it is asked if the papillæ exist also in the deep-seated
parts of this system. Analogy indicates it, since the sensibility is
as great there as at their origin, though with varieties that we shall
point out; but inspection proves it in a manner not less certain. I
think that the villi with which we everywhere see them covered are
nothing but these papillæ.

Very different ideas have been entertained of the nature of these
villi; they have been considered in the stomach and the œsophagus as
destined to the exhalation of the gastric juice, in the intestines as
serving for the absorption of chyle, &c. But, 1st, it is difficult
to conceive how an organ everywhere nearly similar, can perform in
different parts functions so different; I say nearly similar, for we
shall see that these papillæ exhibit differences of length, size,
&c. without having any of texture or structure. 2d. What can be the
functions of the villi of the pituitary membrane, of the internal
coat of the urethra, the bladder, &c. if they have not relation to
the sensibility of these membranes? 3d. The microscopical experiments
of Leiberkuhn upon the vesicle of the intestinal villi have been
contradicted by those of Hunter, of Cruikshank and especially of
Hewson. I am certain that I have never seen any thing similar on the
surface of the small intestines, at the time of chylous absorption; and
yet it would appear that a thing of inspection could not vary. 4th. It
is true that these intestinal villi are everywhere accompanied by a
vascular net-work, which gives them a red colour very different from
the colour of the cutaneous papillæ; but the non-appearance of the
cutaneous net-work is owing to the pressure of the atmospheric air, and
especially to the contraction which it occasions in the small vessels.
Observe in fact the fœtus as it comes from the womb of its mother;
its skin is as red as the mucous membranes, and if its papillæ were a
little longer, it would resemble almost exactly the internal surface
of the intestines. Who does not know moreover, that the vascular
net-work surrounding the cutaneous papillæ, is rendered evident by fine
injections, so as to change their colour entirely?

That in the stomach this vascular net-work continuous with the
exhalants furnishes the gastric juice, and that in the intestines it
intermixes with the origin of the absorbents, so that these embrace
the villi, we cannot doubt after the experiments and observations of
anatomists who have recently engaged themselves in investigating the
lymphatic system. But this does not prevent the base of these villi
from being nervous, and them from performing upon the mucous membranes
the same functions that the papillæ do upon the cutaneous organ.
This manner of regarding them by explaining their existence generally
observed upon all the mucous surfaces, appears to me to be much more
conformable to the plan of nature, than to suppose them in each place
with different and often opposite functions.

Besides it is difficult to decide the question by ocular observation.
The delicacy of these elongations conceals their structure, even
from our microscopical instruments, agents from which anatomy and
physiology do not appear to me to have derived much assistance, because
when we see obscurely, each sees in his own way and according to
his own wishes. It is then the observation of vital properties that
should especially guide us; now, it is evident to judge by them, that
the villi have the nature I have attributed to them. The following
experiment served to demonstrate to me the influence of the papillary
body upon the cutaneous sensibility; it succeeds also upon the mucous
membranes. Remove the epidermis in any part and irritate the papillary
body with a sharp stilet; the animal is agitated, cries out and gives
marks of acute pain. Slide afterwards, through a small opening made in
the skin, a pointed stilet into the sub-cutaneous cellular texture, and
irritate the internal surface of the corion; the animal remains quiet
and makes no noise, unless some nervous filaments accidentally struck
make him suffer. Hence it follows very evidently, that it is upon the
external surface of the skin that its sensibility resides, that the
nerves pass through the corion without contributing to its texture, and
that their expansion takes place on the papillary body. It is precisely
so with the mucous surfaces. Observe that this circumstance coincides
very well with the functions of the two surfaces, which receive by
their free portion the action of external bodies, to which they are
foreign by their adhering portion.

The papillæ exhibit very great varieties. On the tongue, in the small
intestines, in the stomach and in the gall-bladder, they are remarkable
for their length. The œsophagus, the large intestines, the bladder,
all the excretory ducts have those that are less evident; these last
especially and the urethra in particular, are almost smooth in their
whole mucous surface. We can scarcely distinguish the papillæ in the
frontal, sphenoidal, maxillary sinuses, &c.

These small nervous eminences are sufficiently distinct and separate
upon the tongue. In the nasal fossæ, the stomach and the intestines,
they are so near together and at the same time so delicate, that the
membrane has at first view an uniform and smooth appearance, though
it is covered with these elongations. Each papilla is simple; no
bifurcation is ever observed at its extremity. All appear to have a
pyramidal form, if we can judge at least by those which are the most
evident.

Are they susceptible of a species of erection? It has been believed
with regard to those of the tongue, which become erect, it is said, to
perceive tastes, and with regard to those of the nose, which receive
odours more efficaciously in this state of erection, which is in the
sensitive phenomena on a small scale, what the erection of the corpora
cavernosa is on a large one. I do not believe that any exact experiment
can prove this fact. Moreover, it would be necessary then that the
intestinal, vesical papillæ, &c. should be in permanent erection, since
they are almost always in contact with foreign substances.


II. _Parts common to the Organization of the Mucous System._

Besides the blood vessels, the exhalants and the absorbents which
contribute to the structure of this system as to that of all the
others, it exhibits also a common organ, which is found almost always
separate elsewhere, but which is here especially designed for it. This
common organ is of a glandular nature; we shall now examine it.


_Of the Mucous Glands and of the Fluids which they secrete._

The mucous glands exist in all the system of this name. Situated
beneath the corion or even in its thickness, they pour out incessantly
through imperceptible openings a mucilaginous fluid which lubricates
its free surface, and which defends it from the impression of the
bodies with which it is in contact, and at the same time favours the
course of these bodies.

These glands are very apparent in the bronchia, palate, the œsophagus
and the intestines, in which they take the names of the anatomists who
have accurately described them, and where they make in many places
evident projections upon the mucous surface. They are less apparent in
the bladder, the womb, the gall-bladder, the vesiculæ seminales, &c.
but the mucus that moistens them clearly demonstrates their existence.
In fact, since on the one hand this fluid is analogous on all the
mucous surfaces, and, on the other, in those in which the glands are
apparent, it is evidently furnished by them, it must be secreted in the
same way in those in which the glands are less evident. The identity
of the secreted fluids supposes in fact the identity of the secretory
organs. It appears that where these glands are hidden from our view,
nature compensates for their delicacy by their number. Besides, there
are animals in which, in the intestines especially, they form by their
vast number, a kind of new layer, in addition to those of which we
have spoken. In man this is remarkable in the palatine arch, in the
pillars of the velum, on the internal surface of the lips, the cheeks,
&c. &c. There is then this great difference between the mucous and the
serous membranes, that the fluid which lubricates one is furnished by
secretion, whilst that which moistens the others is from exhalation.

The size of the mucous glands varies; those of the velum of the palate,
those of the mouth, &c. are the largest; they become insensible in
the greatest number of mucous surfaces. I dissected two subjects that
died of a pulmonary catarrh, and in them the glands of the trachea and
bronchia, which are, as we know, very apparent, were not enlarged; the
membrane alone appeared to be affected. Besides, we do not yet know the
injuries of these glands, like those of the analogous organs, which
are more apparent from their size. They are in general of a rounded
form but with many varieties. No membrane appears to cover them. They
have, like the salivary glands and the pancreas, only the cellular
texture for an envelope. Their texture is more dense and compact than
these last glands; but little cellular texture is found in them; they
are soft, vascular, and appear when opened very much like the prostate
gland. I cannot say whether nerves penetrate them; analogy indicates
it, for all the principal glands receive them.


_Mucous Fluids._

We know but little of the composition of the mucous fluids, because
in the natural state, it is difficult to collect them, and in the
morbid, in which their quantity increases as in catarrhs for example,
this composition is probably changed. We know that in general they
are unsavoury, insipid, and but slightly soluble in water, in that
even which is raised to the highest temperature; they become putrid
with difficulty. In fact they remain a long time unchanged in the
nose, exposed to the contact of a moist air; in the intestines, they
serve, without danger to them, as an envelope for putrid substances,
&c. taken from the body and subjected to different experiments, they
give results conformable to these facts. All the acids act upon them
and colour them differently; exposed to a dry air, they thicken by
evaporation, and are often even reduced to small shining laminæ. The
nasal mucus especially exhibits this phenomenon. Fourcroy has given
in detail the analysis of this mucus; he has also given that of the
tracheal mucus. But we must not apply rigorously to the analogous
fluids our knowledge of the composition of these. It is sufficient
in fact to examine a certain number of these fluids, to be convinced
that they are not the same in any two places, that more or less thick,
more or less uniform, different in their colour, their odour even, &c.
they vary in the principles that constitute them, as the membranes
which furnish them vary in their structure, in the number and size
of their glands, in the thickness of their corion, the form of their
papillæ, the state of their vascular and nervous systems, &c. I am far
from being certain that the gastric juice is a mucous juice; it is
even probable that exhalation furnishes it, the glands of the stomach
throwing out a different fluid by the way of secretion. But this
assertion is not accurately demonstrated, and perhaps hereafter it will
be proved that this juice, so different from the other mucous juices,
is however one of them, and that its properties are distinct only
because the structure of the mucous surface of the stomach is not the
same as that of the other analogous surfaces.

The functions of the mucous fluids in the animal economy are not
ambiguous. The first of these functions is to defend the mucous
membranes from the impression of the bodies with which they are in
contact, and all which, as we have observed, are heterogeneous to that
of the animal. These fluids form upon their respective surfaces a
layer which supplies, to a certain extent, by its extreme tenuity, the
absence of their epidermis. Thus where this membrane is very apparent,
as upon the lips, the glans penis, at the entrance of the nose and in
general at all the origins of the mucous system, these fluids are not
very abundant. The skin has only an oily layer, infinitely less evident
than the mucous of which we are treating, because its epidermis is very
distinct.

This use of the mucous fluids explains why they are more abundant
where heterogeneous bodies remain some time, as in the bladder, at the
extremity of the rectum, &c. than where these bodies are only to pass,
as in the ureters, and the excretory ducts generally.

Hence why when the impression of a body would be injurious, these
fluids are poured out in greater quantity upon their surfaces. The
sound which enters the urethra and remains in it, the instrument that
is left in the vagina to compress a polypus, that which remains some
time with the same view in the nasal fossæ, the canal fixed in the
lachrymal sac to remove the obstruction, that which is introduced into
the œsophagus to assist interrupted deglutition, always produce, upon
the portions of the mucous surface that corresponds to them, a more
abundant secretion of the fluid which is constantly poured out, a true
catarrh. This is one of the principal reasons that renders it difficult
to keep elastic sounds in the wind-pipe. The abundance of the mucus
that is then secreted, by closing the openings in the instrument,
renders frequent introductions necessary, and can even threaten the
patient with suffocation, as Desault himself has observed, though
however he obtained great advantage from this means, as I have shown
in his surgical works. I ought even to say, that since the publication
of the Treatise on the Membranes, I attempted to fix a sound in the
air tube of a dog, and that the animal died at the end of some time,
having the bronchia filled with a frothy fluid which appeared to have
suffocated him.

It appears then that every considerable excitement of the mucous
surfaces produces a remarkable increase of action. But how can this
excitement, which does not take place immediately upon the gland,
have so great an influence upon it? for, as we have said, these
glands are always under the membrane, and consequently separated
by it from the irritating bodies. It appears that it is owing to a
general modification of the glandular sensibility, which is capable of
being brought into action by any irritation upon the extremity of the
excretory ducts, as I shall prove in the glandular system.

It is to the susceptibility that the mucous glands have of feeling the
irritation made at the extremity of their ducts, that must be referred
the artificial catarrhs with which Vauquelin has been affected by
respiring the vapours of the oxy-muriatic acid, the mucous discharge
that attends the presence of a polypus, of any tumour in the vagina,
of a stone in the bladder, &c. the frequency of fluor albus in women
who are immoderate in the use of sexual intercourse, the more abundant
discharge of the mucus from the nostrils of those who take snuff, &c.
In all these cases, there is evidently excitement at the extremity of
the mucous ducts. I refer also to this excitement the mucous discharge
that takes place, from stimulating the end of the nipple of a woman who
does not give suck, the copious secretions which the presence of an
irritating body produces in the intestines, secretions which especially
furnish the matter of diarrhœas, the gastric derangements which succeed
an indigestion that has allowed to remain on the mucous surface of the
stomach substances not digested and consequently irritating; these
derangements are in fact real catarrhs of the membrane of the stomach,
catarrhs which most often are not connected with bilious turgescence.
I could add many other examples of the mucous secretions increased by
an irritation upon the surface of the membranes, at the extremity of
the excretory ducts; these will be sufficient to give an idea of the
others.

All these excitements produce a kind of inflammation, the peculiarity
of which is to contract at first for some time the glandular ducts, and
arrest the secretion, which they afterwards excite in great quantity.
When the mucous fluids have flowed abundantly for some time, they
gradually diminish though the cause continues; thus less mucus is
discharged from the urethra in proportion after the sound has remained
in it a month, than when first introduced; but almost always as long as
the cause continues, the mucous discharge is greater than in a natural
state.

Blisters are much employed in medicine on the cutaneous organ, to
dispel, according to some, the morbific humour, and overcome, according
to others, a natural irritation by an artificial one. Why should we
not also in many cases irritate the mucous surfaces? why not act upon
the pituitary membrane, upon the glans penis, upon the membrane of the
urethra, upon the pharynx, &c. and especially upon the uvula which is
so sensible? why, instead of epispastics upon the perineum and sacrum,
should we not introduce a sound into the urethra for a paralysis of the
bladder? Instead of acting in hemiplegia upon the cutaneous organ, I
have already twice employed the following means; I have introduced a
sound into the urethra, one in each nasal fossa, and at the same time,
a surgeon irritated at intervals the uvula; the patients appeared to be
much more excited than by blisters. Very strong purgative enemas and
emetics prove the advantage of the excitement of the mucous membranes
in this case. Would it not often be better in ophthalmia, to produce
an artificial catarrh in the nostril of the diseased side, than to
put a blister or seton in the neck? I have once tried it; it did not
succeed; but the ophthalmia was of long standing; I propose to repeat
these experiments at the Hôtel Dieu upon a great number of patients. I
think that we might often in diseases make use of mucous excitements
instead of cutaneous, with much more advantage, because in the mucous
system the contact of a body is sufficient, and it is not necessary to
produce, by removing the epidermis, a kind of ulcer.

The mucous membranes by the continual secretion of which they are
the seat, enjoy a principal part in the animal economy. We ought to
consider them as one of the great emunctories by which the residue of
nutrition constantly escapes, and consequently as one of the principal
agents of the habitual decomposition which removes from living bodies
the particles that, having for some time contributed to the composition
of the solids, are afterwards to become heterogeneous to them. Observe
in fact that the mucous fluids do not enter the circulation, but go out
of the body; that of the bladder, the ureters and the urethra, with
the urine; that of the vesiculæ seminales and the different ducts with
the semen; that of the nostrils by the act of blowing the nose; that
of the mouth, in part by evaporation and in part by the anus with the
excrements; that of the bronchia, by pulmonary exhalation, which arises
principally, as I shall say, from the solution of this mucous fluid in
the inspired air; those of the œsophagus, the stomach, the intestines,
the gall-bladder, &c. with the excrements, of which they often form
in the ordinary state a part almost as considerable as the residue
of the aliments, and which they even compose almost entirely in some
cases of dysentery and fever, in which the quantity of matter voided
is evidently disproportioned to that taken in, &c. Let us observe upon
this subject that there are always some errors in the analyses of the
fluids in contact with the membranes of which we are speaking, as in
that of the urine, the bile, the gastric juices, &c. because it is very
difficult and even impossible to separate the mucous fluids from them.

If we recollect what has been previously said upon the extent of the
two general mucous surfaces, which is equal and even superior to the
extent of the cutaneous organ, and if we afterwards consider that
these two great surfaces are constantly throwing out mucous fluids, we
shall perceive how important this evacuation must be in the economy,
and of what mischief its derangement must become the source. It is
undoubtedly to this law of nature which wishes to have every mucous
fluid thrown out, that must be attributed, in part in the fœtus, the
presence of the unctuous fluid of which the gall-bladder is full, the
meconium which loads the intestines, &c. fluids which appear to be but
a mass of mucous juices, which being unable to pass off, remain until
birth, without being absorbed, upon the respective organs on which they
have been secreted.

The mucous fluids are not the only ones that are thrown out, and are
in this way excrementitious substances to the economy; this is the
case with almost all the fluids separated from the mass of blood by
secretion; this is evident as it respects the greatest part of the
bile; probably the saliva, the pancreatic juice and the tears are
also thrown out with the excrements, and their colour alone prevents
them from being distinguished like the bile. I do not even know if,
by reflecting on many phenomena, we might not attempt to establish as
a general principle, that every fluid separated by secretion does not
enter the circulation again, that this phenomenon belongs only to the
fluids separated by exhalation, as those of the serous cavities, of the
articulations, of the cellular texture, of the medullary organ, &c.
that all the fluids are thus either excrementitious or recrementitious,
and that no one is excremento recrementitious as the common division
implies. The bile in the gall-bladder, the urine in the bladder, the
semen in the vesiculæ seminales, are certainly absorbed; but it is not
the fluid itself which re-enters the circulation; it is only its most
delicate parts, some of its principles which we do not exactly know,
probably the serous and lymphatic part; this does not resemble the
absorption of the pleura and other analogous membranes, in which the
fluid re-enters the blood as it came out of it.

That which is certain on the subject of the excretion of the secreted
fluids is, that I have never been able to produce absorption of the
bile by the lymphatics by injecting it into the cellular texture of
an animal; it produces there inflammation and afterwards suppuration.
We know that urine effused is not absorbed and that it destroys every
part it touches, whilst that effusions of lymph and blood are easily
discussed. There is as it respects the composition an essential
difference between the blood and the secreted fluids. The exhaled
fluids on the contrary, as the serum, in this respect resemble it very
much.

Another very evident proof that all the mucous fluids are designed to
be thrown out, is, that when they have continued for some time in any
quantity upon their respective surfaces, they create there a painful
sensation of which nature relieves us by various means. Thus the
cough, which is the constant result of an accumulation of mucus in the
bronchia, serves to expel it; thus vomiting in gastric derangements
answers the same purpose as it respects the mucous juices accumulated
in the stomach, whose presence produces a weight and even pain, though
the membranes be not affected. We cough at will, because it is the
diaphragm and intercostals by which this function is performed; we do
not seek in medicine for any means to excite it. But as we cannot vomit
at will, and as the presence of mucous juices often by fatiguing the
stomach, does not irritate it sufficiently to produce a contraction,
art has recourse to various emetics. We know what a painful sensation
of weight the continuance of mucus accumulated in the frontal,
maxillary, sinuses, &c. occasions, when there is a catarrh of a portion
of the pituitary membrane. The region of the bladder is for the same
reason, in catarrhs of this organ, the seat of a troublesome and even
painful sensation.

In general, the sensation which arises from the presence of the
mucous juices remaining too long and in too great quantity upon their
respective surfaces, varies because, as we shall see, each part of
the mucous system has its peculiar mode of sensibility; so that the
pain is not the same in each, though produced by the same cause. I
would only observe that this sensation does not resemble that which
arises from the tearing or the acute irritation of our parts; it is an
uneasy, inconvenient sensation, difficult to be borne. Every one knows
that which arises from mucus accumulated in the nasal fossæ, when the
nose has not been blown for a long time, that disagreeable one that
accompanies gastric derangements, &c. Those who have a weakness of
the lachrymal sac in which the tears, on account of this, accumulate
during the night, wake up with a sensation of weight, of which they are
relieved by evacuating the sac by pressure, if the puncta lachrymalia
are open.


_Blood Vessels._

The mucous membranes receive a very great number of vessels. The
remarkable redness that distinguishes them would be sufficient to
prove it, if injections did not demonstrate it; this redness is not
everywhere uniform. It is almost nothing in the sinuses of the face, in
the internal ear, of which the membranes are rather whitish, and which
appear so especially, because their extreme delicacy allows the bone
upon which they are applied to be seen very distinctly. In the bladder,
in the great intestines, in the excretories, &c. this colour, though
still very pale, is a little more evident; it becomes very much so in
the stomach, the small intestines, the vagina and in the pituitary and
palatine membranes. In the gall-bladder we cannot distinguish it,
because the bile always covers the mucous surface in the dead body.

This colour depends upon a very extensive vascular net-work, the
branches of which, after having passed through the mucous corion,
and ramifying there, divide and spread ad infinitum on its surface,
embracing the papillary body and covered only by the epidermis.

It is the superficial position of these vessels and consequently
their want of support on one side, that exposes them frequently to
ruptures from considerable shocks, as happens on the surface of the
bronchia from a severe cough, on that of the ear and the nose from a
violent blow on the head. We know that hemorrhage of the mucous system
bordering on the brain, is a common accident from concussions and
wounds of the head. Hence why the least gravel makes the ureters bleed;
why one of the signs of stone in the bladder is the passing of blood;
why a blunt sound carefully introduced is so often withdrawn bloody
from the urethra; why the least effort made with instruments carried
upon polypi, into a fistula lachrymalis or into the nostrils, produces
hemorrhage. I have already observed that we must carefully distinguish
these hemorrhages from those furnished by the exhalants, and which do
not suppose any vascular rupture.

It is also the superficial position of the vessels of the mucous
system, which makes its portions visible, as the red edge of the
lips, the glans penis, &c. often serve to show us the state of the
circulation. Thus in the different species of asphyxia, in submersion,
strangulation, &c. these parts are remarkably livid, an effect of the
passage of the venous blood, which has undergone no change from the
want of respiration, into the extremities of the arterial system.

The long continued exposure of the mucous system to the air, often
makes it lose the redness that characterizes it, and it then
assumes the appearance of the skin, as has been observed by Sabatier
in treating of prolapsus of the womb and vagina, which, from this
circumstance, have sometimes so misled some people, as to make them
believe it a case of hermaphrodism.

An important question presents itself in the history of the vascular
system of the mucous membranes, viz. whether this system admits more
or less blood according to different circumstances. As the organs
within which these membranes are spread, are almost all susceptible of
contraction and dilatation, as we see in the stomach, the intestines,
the bladder, &c. it has been thought that during the dilatation, the
vessels being more expanded, receive more blood, and that during the
contraction on the contrary, being folded up, as it were choaked,
they admit but a small quantity of this fluid which then flows into
the neighbouring organs. Chaussier has made an application of these
principles to the stomach, whose circulation he has considered as being
alternately inverse of that of the omentum, which receives during the
vacuity of this organ, the blood which this when it is contracted
cannot admit. An analogous use has also been attributed to the spleen
since the time of Lieutaud. The following is what the inspection of
animals opened during abstinence and at different periods of digestion,
has shown me upon this point.

1st. During the fulness of the stomach the vessels are more apparent on
the exterior of this viscus, than when it is empty. Within, the mucous
surface is not more red, sometimes it has appeared to me to be less
so. 2d. The omentum, less extended during the fulness of the stomach,
exhibits nearly the same number of vessels, as long, but more tortuous,
than when it is empty. If they contain less blood, the difference is
hardly sensible. I would observe, that in order to distinguish this
well, it is necessary to take care that in opening the animal, the
blood does not fall on the omentum which presents itself, and thus
prevent its state from being ascertained. This is besides a necessary
consequence of the arrangement of the vascular system of the stomach.
In fact the great stomachic coronary being situated transversely
between it and the omentum, and furnishing branches to each, it is
evident that when the stomach is lodged between the layers of the
omentum by separating these layers, and this by applying itself upon
it becomes shorter; it is evident, I say, that the branches which it
receives from the coronary cannot be equally applied to it also. In
order to do this, it would be necessary that they should go from one
to the other without the intermediate trunk that cuts them at right
angles; then, in distending, the stomach would separate them as it
does the omentum, and would be lodged between them; whereas it pushes
them before it with their common trunk, the stomachic coronary, and
makes them fold. 3d. I am confident that there is no such constant
relation between the size of the spleen and the emptiness or fulness
of the stomach, and that these two circumstances coincide necessarily,
and that if the first organ increases or diminishes under different
circumstances, it is not always precisely the reverse of the stomach.
I first made, like Lieutaud, experiments upon dogs to convince myself
of it; but the inequality in the size and age of those that were
brought to me, making me fear that I should not be able to compare
their spleens correctly, I repeated them upon guinea-pigs of the same
litter and size, and examined at the same time, some when the stomach
was empty and others when it was full. I have almost always found the
size of the spleen nearly equal, or at least the difference was not
very sensible. Yet in other experiments, I have seen under various
circumstances, inequalities in the size of the spleen and especially
in the weight of this viscus; but it was indifferently during or after
digestion.

It appears from all this, that if during the vacuity of the stomach,
there is a reflux of blood towards the omentum and spleen, this reflux
is less than it has been commonly said to be. Besides during this
state of vacuity, the numerous folds of the mucous membrane of this
viscus leaving it, as we have said above, almost as much surface and
consequently as many vessels as during fulness, the blood can circulate
in it almost as freely. It has no real obstacles but in the tortuous
courses, and not in the obstruction, compression and choaking of these
vessels by the contraction of the stomach; now this obstacle is easily
surmounted, or rather it is not one as I have proved in my Researches
upon Death. As to the other hollow organs, it is difficult to examine
the circulation of the neighbouring parts during their fulness and
vacuity, as the vessels of these are not superficial as in the omentum,
and as they themselves are not insulated like the spleen. We can only
then, to decide the question, see the state of the mucous membranes on
their internal face; now this face has always appeared to me to be as
red during the contraction as during the dilatation.

Besides I only give this as a fact without pretending to draw from it
any consequence in opposition to the common opinion. It is possible in
fact that though the quantity of blood may be nearly always the same,
the rapidity of the circulation being increased, more of this fluid may
consequently in a given time enter it when it is full; which appears
to be necessary to the greater secretion that then takes place of the
mucous fluids, a secretion excited by the presence of the substances in
contact with the surfaces of the same name. For example, there is no
doubt that there is three or even four times as much mucus secreted in
the urethra, when a sound fills it, as when it is empty; now the blood
must be in proportion.

The remarkable redness of the mucous system, the analogy of respiration
in which the blood flows through the mucous surface of the bronchia
the well known experiment of a bladder filled with blood and immersed
in oxygen, by which means the blood becomes red, have induced a belief
that the blood being separated from the atmospheric air only by a thin
pellicle or some of the mucous surfaces, as upon the pituitary, the
palatine, the glans penis, &c. assumed there a redder colour, either
from getting rid of a portion of its carbonic acid gas, or by combining
with the oxygen of the air, and that these membranes thus performed
functions accessory to those of the lungs. The experiments of Jurine
upon the cutaneous organ, experiments adopted by many celebrated
philosophers, seem to strengthen this conjecture.

I tried the following experiment to ascertain this fact. I drew through
a wound made in the abdomen a portion of intestine which I tied at one
point, I afterwards reduced it, keeping out a small portion only which
I opened and by which I introduced atmospheric air, which filled the
whole portion situated on this side of the ligature. I afterwards tied
the intestine below the opening, and reduced the whole of it. At the
end of an hour, the animal being opened, I compared the blood of the
mesenteric veins which arose from the portion of intestine distended
with air, with the blood of the other mesenteric veins arising from the
rest of the canal. No difference of colour was manifest; the internal
surface of the distended portion of the intestine was not of a more
brilliant red. I thought I should obtain a more evident effect, by
repeating with oxygen the same experiment upon another animal; but I
perceived no greater variety in the colour of the blood. As upon the
mucous membranes which are ordinarily in contact with the air, this
fluid is constantly changing and is agitated by a perpetual motion,
and as in the preceding experiment it remained stagnant, I attempted
to produce the same effect in the intestines. I made two openings in
the abdomen, and drew out at each a portion of the intestinal canal;
having opened these two portions, I fitted to one the tube of a bladder
full of oxygen and to the other that of an empty bladder; I afterwards
compressed the full bladder, so as to make the oxygen pass into the
other, by going through this portion of intestine, left in the abdomen
that the heat might support the circulation in it. The oxygen was
thus many times sent from one bladder to another, taking its course
through the intestine, which, on account of its contractility is more
difficult than it at first seems to be. The abdomen being afterwards
opened I found no difference between the venous blood returning from
this portion of intestine, and that which flowed from the others. The
superficial position of the mesenteric veins, covered only by a fine
and transparent layer of peritoneum, their size, if the animal be
rather large, render this sort of comparison very easy.

I perceive that we cannot infer from what takes place in the
intestines, what happens in the pituitary, palatine membrane, &c.
because though analogous, the organization may be different. We cannot
here as in the intestines examine the venous blood returning from the
part; but, 1st, if we consider that in animals who have respired oxygen
for some time, we see the palatine and pituitary membranes more red;
2d, if we reflect that the lividity of the different parts of this
membrane, in those destroyed by asphyxia by the carbonic acid gas,
depends not on the immediate contact of this gas upon the membrane,
but upon the passage of venous blood into the arterial system, as my
experiments have, I think, demonstrated; 3d, if we remark finally
that in these circumstances the contact of the air does not change,
after death, the lividity which the venous blood gives to the mucous
membranes, although the skin be then much more permeable to every
kind of aeriform fluid; we shall see that it is at least necessary to
suspend our judgment upon the colouring of the blood in the mucous
membranes, until further observations have decided the question.

The following experiment may also throw some light upon the subject.
I have inflated the peritoneal cavity of several guinea-pigs with
carbonic acid gas, with hydrogen, oxygen and atmospheric air, to see if
I could effect through a serous membrane what I could not make succeed
in a mucous; I have not, after these experiments, found any difference
in the colour of the blood of the abdominal system; it was always the
same as in the common guinea-pig which I killed for comparison.

I think however that I have remarked many times, both in frogs and
animals with red and warm blood, such as cats and guinea-pigs, that
the infiltration of oxygen into the cellular texture gives, at the end
of some time, a much brighter colour to the blood, than that which
this fluid exhibits in artificial emphysemas produced by carbonic
acid gas, hydrogen and atmospheric air, in all which the colour of
the blood scarcely differs at all from what is natural. But in other
cases oxygen has had no influence upon the colour of the blood; so
that notwithstanding having made many experiments upon this point, I
am unable to give any general result. It appears that the tonic forces
of the cellular texture and of the parietes of the vessels which are
spread upon this texture, receive a very variable influence from
the contact of the gases, and that according to the nature of this
influence, the fibres crisping and contracting more or less, render
these parts more or less permeable, either to the aeriform fluids
that tend to escape from the blood in order to unite with that of the
emphysema, or to this last fluid, if it tends to combine with the
blood, which no doubt produces the varieties I have observed.

The red colour of the mucous system is analogous to that of the
muscular system. It does not depend essentially on the blood
circulating in the small arteries of this system. It arises from
the colouring portion of the blood combined with the mucous texture,
especially in the deep part of the organs; for at the origin of the
mucous surfaces, this colour appears to be principally owing to the
blood in circulation; in fact asphyxia does not render so livid the
deep mucous surfaces, as it does those which are superficial and in
communication with the skin. The black blood arrives immediately to
these by the last arteries, and tinges them as we see. In syncope in
which the heart being affected no longer sends blood into the arteries,
we know that this portion of the mucous system becomes instantly white.

Besides the red colour of the deeper portions, can, like that of the
muscles, be removed by repeated washing and frequently changing the
water. Yet the water in which they have been washed is not as red as
that used for the muscles.

The instant a mucous surface is plunged into boiling water, however
red it may be, as that of the intestines and the stomach, it instantly
whitens. The action of the nitric, sulphuric and muriatic acids
produces in it also a sudden whiteness.

This colour of the mucous surfaces acquires a remarkable intensity in
inflammation. The redness becomes then extremely deep on account of the
quantity of blood that is accumulated in the capillary system. It is
particularly in dysentery that the internal surface of the intestines
exhibits this phenomenon in a striking degree. I ought however to
observe to those who open dead bodies, that they never should lose
sight of the original tinge of the portion of the mucous system they
examine, since each of the divisions of this system exhibits in its
shades remarkable differences. If the membrane of the bladder, the
rectum, &c. is found as red as that of the stomach in its natural
state, then pronounce that there had been inflammation; if the redness
of the sinuses equals that which is natural to the bladder and the
rectum, decide that inflammation had existed in them. There is, as
I have said, a scale of colour for the mucous system. It is then
essential to have an accurate knowledge of this scale, a type to which
we can refer the inflammatory state in the examination of dead bodies.


_Exhalants._

Does exhalation take place upon the mucous surfaces? The analogy of the
skin seems to indicate it; for it is well proved that the sweat is not
a transudation through the inorganic pores of the cutaneous surface,
but a real transmission by vessels of a peculiar nature and continuous
with the arterial system.

It appears at first that the pulmonary perspiration which takes place
upon the mucous surface of the bronchia, which has so much relation
with that of the skin, which increases and diminishes according as this
diminishes or increases, and the matter of which is probably of the
same nature; it appears, I say, that the pulmonary perspiration is made
at least in great part by the system of exhalant vessels, and that if
the combination of the oxygen of the air with the hydrogen of the blood
contributes to produce it, during the act of respiration, it is but
in very small quantity, and it is the portion that is purely aqueous.
Besides, this last hypothesis of modern chemists, contradictory to the
production of all the other fluids thrown out by the mucous surfaces,
appears to me ill adapted to explain the formation of this. When the
same phenomenon is produced in many places, and the explanation that is
given of it is applicable only to one, we should be suspicious of this
explanation.

It should be observed in regard to the pulmonary perspiration, that the
solution of the mucous fluid which lubricates the bronchia, in the air
constantly inspired and expired, furnishes a considerable portion of
this vapour which, insensible in summer, is very evident in winter, on
account of the condensation of the air. The mucous juices are dissolved
like every other fluid; for wherever there is atmospheric air, heat and
moisture, there is evaporation. Here this evaporation is even a means
which nature employs to rid herself, as I have said, of the mucous
juices. If they are too abundant, as in a cold, then the quantity of
air which serves as a vehicle to them, not increasing in proportion,
it is necessary that there should be another mode of evacuation; this
is expectoration which compensates for what the air cannot remove by
solution.

The intestinal juice which Haller has especially considered, but
which appears to be in much less quantity than he thought it, the
œsophagean and gastric juices, particularly this last which has been
supposed to be distinct from the mucous juices, are probably deposited
by exhalation upon their respective mucous surfaces. But in general
it is very difficult to distinguish with precision what belongs in
these organs to the exhalant system, from that which is furnished by
the system of mucous glands, which, as we have said, are everywhere
subjacent to them. Thus we constantly see the mucous fluids of the
œsophagus, the stomach and the intestines, mixing with the œsophagean,
gastric and intestinal fluids.

As on the one hand the blood vessels ramify almost naked on the mucous
surfaces, and as on the other these vessels are always the origin of
the exhalants, it is evident, that these have but a short course to
run to arrive at their surfaces; they are rather pores than distinct
vessels. Hence why no doubt the blood has so great a tendency to escape
by the exhalants; why consequently hemorrhages without rupture are so
frequent in the mucous system; why this affection can be classed in
the diseases of this system, &c. &c. No other, by the arrangement of
the arteries, offers to the exhalants so short a course between their
origin and termination. Often even, as I have said, we make the blood
of these vessels ooze in the dead body through their exhalants.


_Absorbents._

The absorption of the mucous membranes is evidently proved, 1st,
by those of chyle and of drinks on the intestinal surfaces, of the
venereal virus upon the glans penis and the canal of the urethra,
of the variolous when the gums are rubbed with it, of the serous
portion of the bile, the urine and the semen, when they remain in
their respective reservoirs. 2d. When, in the paralysis of the fleshy
fibres that terminate the rectum, substances are accumulated at the
extremity of this intestine, these substances often become hard, an
effect probably of an absorption of the soft parts. 3d. There have been
various cases in which the urine has been almost wholly absorbed by the
mucous surface of the bladder, where there have been insurmountable
obstacles in the urethra. 4th. If we respire, by means of a tube,
the air of a large vessel filled with the exhalations of turpentine,
so that these vapours can only act upon the mucous surface of the
bronchia, the urine has the peculiar odour that always arises from the
use of this substance, the exhalations from which have been introduced
into the blood by the means of absorption, &c.

Whatever may be the mode of this absorption, it appears that it does
not take place in a constant and uninterrupted manner, like those of
the serous membranes, in which the exhalant and absorbent systems are
in a regular and continual alternation of action. There is scarcely any
but the chylous absorption, that of drinks, and that of the aqueous
portion of the secreted fluids remaining in a reservoir as they come
from their glands, that constantly take place. Nothing is more variable
than the other absorptions. Under the same influence, the glans takes
up or leaves the venereal virus; the internal surface of the bronchia
sometimes admits and sometimes refuses admittance to contagious
miasmata. There are more cases of retention in which the urine is not
absorbed entirely, than there are where this absorption takes place,
&c. &c. The innumerable varieties of the vital forces of the mucous
membranes, varieties produced by those of the stimuli with which they
are in contact, explain these phenomena. If these forces are raised
or diminished a little, the absorption is altered, even that which is
natural, as that of the chyle. Take a purgative; it contracts, shuts
even the mouth of the absorbents of the intestinal canal; as long as
the irritation continues, all the drinks that are taken pass off by
the anus; at the end of four or five hours, the absorbents gradually
recover their natural tone and absorption recommences. In these cases,
the first discharges are only the intestinal matters, the others are
the copious drinks that have been taken. There are many diseases in
which, the sensibility of the chylous absorbents being too much raised,
they are no longer in relation with the aliments, they take up with
difficulty the residue of them, &c. Deficiency of action produces
the same phenomenon; in absorption in fact it is a middle degree of
sensibility of the organ which produces it, a degree below or above
which it cannot take place.

All the mucous absorbents appear to go to the thoracic duct.


_Nerves._

I would remark that at all the origins of the mucous system, where the
animal sensibility is very great and where it places us, like the skin,
in relation with external bodies, cerebral nerves are distributed. The
pituitary and palatine membranes, the conjunctiva, the mucous surface
of the rectum, the glans penis, the prepuce, &c. exhibit this fact very
evidently. There are hardly any nervous filaments coming from the
ganglions in these different places.

On the contrary, this last species of nerves is the predominant one
in the intestines, in all the excretories, in the reservoirs of the
secreted fluids, &c. places where the organic sensibility is the most
evident.


ARTICLE THIRD.

PROPERTIES OF THE MUCOUS SYSTEM.


I. _Properties of Texture._

Extensibility and contractility are much less in this system than
they at first appear to be, on account of the numerous folds which it
exhibits in the hollow organs during their contraction, folds which
are developed only during extension, as we have seen. Yet these two
properties become very evident in some cases. The excretories are
capable of taking a size much larger than is natural to them. This is
seen in the ureters in particular, which are sometimes found as large
as an intestine. The ductus choledochus and the pancreatic duct have
often also these dilatations. The urethra and the salivary ducts appear
to be less extensible than the others. If they have ever so little
obstacles from strictures, contractions, &c. they break rather than
stretch; hence various urinary and salivary fistulas.

Hence there is, as we see, many varieties in the degrees of the
extensibility of the mucous system; it is the same with regard to the
contractility of texture. These two properties are besides capable
of being put rapidly into action. We know that the stomach, the
intestines, the bladder, &c. pass in an instant from a great size
to extreme contraction. Their functions even suppose this rapidity,
without which they could not be performed. The palatine membrane which
lines the cheeks, exhibits the same phenomenon when the mouth is filled
with air, aliments, &c. which are afterwards expelled from it.

When the usual fluids cease to pass through the mucous ducts, they
remain in permanent contraction; this is what takes place in the
intestines below a preternatural anus. I have seen in this case the
cæcum and the rectum reduced to the size of a large quill. Yet there
is never then an obliteration of their parietes, on account of the
presence of the mucous juices, of which the patient always passes
a certain quantity. The urethra, after the operations for stone in
which the urine passes for a long time through the wound, and in the
great fistulas in the perineum or above the pubis, the salivary ducts
in wounds which affect them and through which the whole saliva is
discharged, the nasal canal in fistulæ lachrymales, contract also more
or less, but are never obliterated. We know that the vas deferens is
often a very long time without having semen pass through it, and yet
it remains open. This phenomenon distinguishes the mucous ducts from
the arterial, which, when the course of blood is interrupted in them,
change into ligaments in which every thing like a canal disappears. We
ought not to lose sight of this phenomenon of all the mucous ducts; it
proves the incorrectness of the practice of those who, thinking that at
the end of some time it is impossible to re-establish, in fistulas, the
natural way, think it necessary to make an artificial one.

The mucous tubes are not only not obliterated when they are empty, but
when inflamed they do not even contract adhesions of their parietes,
as so often happens in the serous cavities, in the cellular texture,
&c. Observe how important this fact is to the great functions of life;
what would indeed become of these functions, if in catarrhs of the
intestines, the bladder, the stomach, the œsophagus, the excretories,
&c. these adhesions were as frequent as they are in pleurisy,
peritonitis, pericarditis, &c.


II. _Vital Properties._

Few systems live in a more active manner than this; few exhibit the
vital forces in a higher degree.


_Properties of Animal Life._

Constantly in relation, like the integuments, with external bodies, the
mucous surfaces have occasion for a sensibility which would enable the
mind to perceive these relations, especially at the origin of these
surfaces. Thus the animal sensibility is very much developed there. It
is even superior in it in many places to that of the cutaneous organ,
in which no sensation is as acute as those which take place on the
pituitary membrane from odours, upon the palatine from tastes, upon the
surface of the vagina, the urethra, the glans penis during coition. But
without speaking of these exaggerations of sensibility, if I may so
express myself, all the natural phenomena of the mucous surfaces prove
this property in an evident manner; it is unnecessary however to pause
for these phenomena.

I would only observe that this sensibility, like that of the cutaneous
organ, is essentially subjected to the powerful influence of habit,
which tending constantly to blunt the acuteness of the sensation of
which they are the seat, brings equally to indifference the pain and
the pleasure they make us experience, and of which it is the medium,
as we know. 1st. I say that habit brings to indifference the painful
sensations arising upon the mucous membranes. The presence of a sound
in the urethra for the first time, is distressing the first day,
painful the second, inconvenient the third, and insensible the fourth.
Pessaries introduced into the vagina, bougies into the rectum, tents
fixed in the nasal fossæ, and a canula kept for a length of time in the
nasal canal, exhibit in different degrees the same phenomena. It is
upon this remark that is founded the possibility of the introduction of
sounds into the wind-pipe to aid respiration, and into the œsophagus to
produce an artificial deglutition. This law of habit can even transform
into a pleasure an impression at first painful; the use of snuff
for the pituitary membrane and different aliments for the palatine,
furnish well known examples of this. 2d. I say that habit brings to
indifference agreeable sensations arising on the mucous surfaces; the
perfumer, placed in an odoriferous atmosphere, the cook, whose palate
is constantly affected by delicious tastes, do not find in their
professions the acute enjoyments they give to others. From habit can
even arise the succession from pleasure to painful sensations, as in
the preceding case it converts pain to pleasure.

I would however observe that this remarkable influence of habit is only
exerted upon sensations produced by simple contact, and not upon those
produced by real injuries, as the tearing, the forced stretching, the
cutting or pinching of the mucous system; thus it does not mitigate
the pains caused in the bladder by pressure and by the tearing a stone
occasions, or on the surface of the womb, of the nasal fossæ, &c. by
a polypus, on that of the œsophagus or the wind-pipe by a sharp and
uneven body accidentally lodged there, &c. &c.

It is to this power of habit over the sensibility of the mucous system,
that must be in part referred the gradual diminution of its functions,
which accompanies age. Every thing is stimulant in infancy, every
thing is blunted in old age. In one, the very active sensibility of
the alimentary, biliary, urinary, salivary surfaces, &c. contributes
principally to produce that rapidity with which the digestive and
secretory phenomena succeed each other; in the other, this sensibility
blunted by habitual contact, connects but slowly the same phenomena.

Is it not from the same cause that arises this remarkable modification
of the sensibility of this system, viz. that at its origins, as upon
the pituitary, the palatine membranes, the œsophagus, the glans penis,
the opening of the rectum, &c. it gives us the sensation of the bodies
with which it is in contact, and that it does not give this sensation
in the very deep organs which it lines, as in the intestines, the
excretories, the gall-bladder, &c.? In the interior of the organs,
this contact is always uniform; the bladder only knows the contact
of the urine, the gall-bladder that of the bile, the stomach that of
the aliments masticated and reduced, whatever may be their diversity,
to an uniform, pulpy mass. This uniformity of sensation produces no
perception, because in order to perceive, it is necessary to compare,
and here the two terms of comparison are wanting. Thus the fœtus has no
sensation of the waters of the amnios; thus, the air, very irritating
to a new born infant, becomes insensible to it. On the contrary, at the
beginning of the mucous membranes, the stimulants vary every instant;
the mind can then perceive the presence of them, because it can
establish approximations between their different modes of action. What
I say is so true, that if in the interior of the organs, the mucous
membranes are in contact with a foreign body, different from that which
they are accustomed to, they transmit the sensation of it to the mind.
A catheter in the bladder, sounds introduced into the stomach, &c. are
examples of this. Fresh air, in great heat of the atmosphere, suddenly
introduced into the trachea, carries an agreeable sensation over the
whole surface of the bronchia; but habit soon renders us insensible to
it and we cease to have the perception of it. Yet it is to be observed
that when the intestines come out in preternatural inversions of the
anus, their sensibility never becomes so acute as that of the palatine,
pituitary surfaces, &c. &c. The absence of cerebral nerves no doubt has
an influence upon this phenomenon.

The sensibility of the mucous system is much raised in inflammations;
acute catarrhs are, as we know, very painful. The contact of bodies is
then not only felt, but is very disagreeable. I would observe however
that the sensibility never rises so high as it does in the inflamed
cellular, serous, fibrous systems, &c. A phlegmon, a pleurisy, &c.
compared with a catarrh, are sufficient to convince us of this. We may
say that the organs least accustomed to feel in the natural state,
experience in diseases the most acute sensations.

There is no animal contractility in the mucous system.


_Properties of Organic Life._

Organic sensibility and insensible contractility are very evident in
the mucous system. They are constantly put in action in it by four
different causes; 1st, by the nutrition of this system; 2d, by the
absorption that takes place in it, either naturally or accidentally;
3d, by its exhalation; 4th, by the constant secretion of its glands.
These two properties are the original causes of all these functions,
the increase and diminution of which are truly the indices of the state
of these glands. As a thousand causes continually act upon the mucous
surfaces, as a thousand different stimuli continually excite them,
especially at their origin, this state is incessantly varying like the
functions that result from it.

The mucous system differs then from most of the others; 1st, in
this, that the organic sensibility and the insensible contractility
are habitually more exalted in it, on account of the more numerous
functions over which they preside; 2d, in this, that they incessantly
vary, on account of the variety of the stimuli. Observe in fact that,
in the osseous, fibrous, cartilaginous, muscular, nervous systems, &c.
on the one hand, these properties are put in action only by nutrition;
and on the other, no stimulant being in contact with these systems,
they always remain at the same degree.

Hence it is not astonishing that the diseases which especially put in
action the organic sensibility and the insensible contractility of
the same species, should be so frequent in the mucous organs. All the
catarrhal affections, both acute and chronic, all the hemorrhages,
various and numerous tumours, polypi, fungi, &c. all kinds of
excoriations, ulcers, &c. of which they are the seat, are derived
from the various alterations of which their organic properties are
susceptible.

It is also to these alterations that must be attributed a remarkable
phenomenon, viz. the innumerable varieties the mucous fluids exhibit in
diseases. Take for example those that are thrown off from the internal
surface of the bronchia, those that are brought up by expectoration,
and which we can examine better than others, because they are mixed
with no foreign substance; observe how they differ, in the different
affections of the chest; sometimes they have a yellowish and as it were
bilious tinge; sometimes they are frothy in the vessel which receives
them; sometimes they adhere to it with tenacity, and at others they
are easily detached from it. Viscid or liquid, fetid or without odour,
grey, white, green or even black in the morning, they have a thousand
external appearances which evidently denote differences in their
composition, differences which chemists have not yet explained to us. I
do not speak of the cases where as in phthisis, hemoptysis, &c. foreign
substances are mixed with these mucous juices. Now it is evident that
all these varieties depend only upon the varieties of the organic
sensibility of the bronchial glands or of the membrane upon which they
pour out their fluids. According as the property is differently altered
in the mucous system, it is in relation with different substances,
admits some and rejects others. The same organ, the same vessels can
there, according to the state of the forces that animate them, separate
from the mass of blood many different substances, rejecting one to-day
and admitting it to-morrow, &c.

Do you wish for other proofs of the innumerable varieties which the
different modifications of the organic sensibility of the mucous
membranes produce in their functions? Observe the urethra; in the
ordinary state it lets the urine pass freely; in the excitement in
which its forces are in erection, its sensibility repels it and admits
only the semen. Who does not know that in one species of epiphora,
the mucous passages for the tears are open, and that the diminution
only of their vital forces prevents this fluid from flowing in them?
The sensibility of the mucous surfaces is oftentimes so altered that
their glands refuse to admit every kind of fluid; this happens in the
beginning of some peripneumonies, in which expectoration is entirely
suppressed, it is always a serious beginning, and even an indication
of death, if the state of the sensibility does not change, unless a
relaxation, as it is commonly called, takes place.

In general, I think that there are but few systems which deserve, more
than this of which we are treating, to fix the attention of physicians,
on account of the innumerable alterations of which it is susceptible,
alterations which almost always suppose those of the predominant
vital properties of this system, as the alterations of the muscular,
nervous systems, &c. most often put in action the properties which more
particularly belong to them, viz. animal contractility for one, and the
sensibility of the same species for the other.

The sensible organic contractility does not appear to be the attribute
of the mucous system; yet there is often in it something more than the
insensible oscillations which compose the other organic contractility.
For example, in the emission of semen, in which there is no agent of
impulse at the extremity of the urethra, as in the evacuation of urine,
it is very probable that this is spasmodically contracted to produce
the jet, oftentimes very strong, which then takes place. The following
phenomenon which I have observed in myself appears to belong to the
same cause. In gaping, there sometimes escapes from the mouth then wide
open, a small jet of fluid, which coming from the lateral parts of this
cavity that it passes over, is thrown at some distance; if a surface
is then before the mouth, as when we read a book, this fluid is spread
in small drops upon this surface; it is the saliva which the excretory
duct of Steno throws out with force. Now on the one hand this duct is
almost wholly mucous, and on the other it has not at its posterior
part a muscular agent of impulse. Perhaps the excretories which pour
out their fluids in the deep parts of the organs, exhibit the same
phenomenon. We know that the milk is also sometimes subject to a kind
of ejection, when it is very abundant, an ejection which supposes
a powerful contraction of the lactiferous ducts. In general, these
different motions analogous to that of the dartos, of the cellular
texture, &c. appear to hold a middle place between those of tone and
those of irritability.


_Sympathies._

There are few systems that sympathize more frequently with the others
than this. Now in its sympathies, it sometimes influences and sometimes
is influenced. The first Tissot calls the active mode of sympathy, the
second the passive. Let us make use of this classification.


_Active Sympathies._

One point of the mucous system being inflamed, irritated or stimulated
in any way, all the vital forces can enter separately into action in
the other systems.

Sometimes it is the animal contractility that is brought
sympathetically into action; thus the diaphragm, the intercostal and
abdominal muscles contract to produce sneezing from irritation of the
pituitary membrane, or cough from the irritation of the membrane of
the bronchia, or from that even of the surface of the stomach, which
produces stomachic coughs, which, as we know, have nothing to do with
affections of the chest. We know the general spasm that seizes all the
muscles the instant a foreign body passes between the mucous edges of
the epiglottis. Stones of the bladder and the urethra, by making the
cremaster contract sympathetically, produce retraction of the testicle.
Physicians might, I think, profit by the knowledge of these mucous
sympathies. In apoplexy, in which the bronchia is sometimes filled with
mucus that the patient cannot evacuate, the action of ammonia upon the
pituitary membrane produces the double effect, 1st, of stimulating the
brain as blisters do; 2d, of freeing, by the cough it occasions, the
surface of the bronchia, which being obstructed, is an obstacle to the
passage of the air.

Sometimes it is the animal sensibility that is put into action by an
affection of the mucous surfaces. The stone, that irritates that of the
bladder, causes an itching at the end of the glans penis. That of the
intestines being irritated by worms, an inconvenient itching is felt
at the end of the nose. Whytt has seen a foreign body introduced into
the ear, affect painfully the whole corresponding side of the head; an
ulcer of the bladder, produce every time the patient passed water, a
pain on the superior part of the thigh, &c. &c.

The sensible organic contractility is often sympathetically excited
by the affections of the mucous system. I might at first refer to
this subject what I have observed respecting the organic muscles,
almost all of which move from an excitement of a contiguous mucous
surface; but that is a natural phenomenon; there are many others that
are preternatural. A stone that irritates the internal surface of the
pelvis of the kidney produces vomiting, which is, as we know, produced
any time at will by an irritation of the uvula. The instant the semen
passes the urethra in coition, the action of the heart is commonly
accelerated. Tissot speaks of a stone which, being entangled in the
duct of Warton, produced a sympathetic discharge from the bowels. I
saw at the Hôtel Dieu two women, who, whenever they menstruated, and
the mucous surface of the womb was consequently in activity, could
retain the urine but a short time in the bladder, which contracted
involuntarily to expel it the moment it entered it. At ordinary times,
there was nothing peculiar in the evacuation of this fluid.

As to the sympathies of insensible contractility and of organic
sensibility, they take place when a mucous surface being irritated
towards the extremity of an excretory duct, the gland of this duct is
brought into action, when, for example, the saliva flows in greater
abundance by the action of sialagogues upon the extremity of the
Stenonian duct. Whenever there is a gastric derangement and the mucous
surface of the stomach consequently suffers, the surface of the tongue
is sympathetically affected; the glands situated under this surface
increase their action and hence that white mucous coat, that is
commonly called a foul tongue, which is a real sympathetic catarrh, but
which can however exist idiopathically. Here also is to be referred
the remarkable influence of the mucous system upon the cutaneous; thus
during digestion, in which the mucous juices pour out abundantly from
all sides into the stomach and the intestines, and in which the mucous
membranes of the gastric viscera are consequently in great action, the
fluid of insensible transpiration is lessened remarkably, according to
the observation of Sanctorius; it is in very small quantity three hours
after the meal, so that the action of the cutaneous organ is evidently
less energetic. Thus during sleep, in which all the internal functions
become more evident and are exerted to their utmost, and in which the
sensibility of the mucous membranes is consequently strongly developed,
the skin seems to be struck with a species of atony; it becomes cold
more easily, it allows less substances to escape from it, &c. To
these sympathies also can be referred many phenomena of hemorrhages.
We know with what facility the mucous surface ceasing, from any
accidental cause, to throw out blood, as happens so often on that of
the womb, another is immediately affected and discharges this fluid;
hence hemorrhages from the nose, the stomach, the chest, &c. from the
suppression of those of the uterus, &c.


_Passive Sympathies._

In many cases, the other systems being irritated, the animal
sensibility of this is brought into action. Among the numerous examples
of this fact, the following is a remarkable one. In many diseases in
which organs foreign to the mucous system are affected, we experience
a sensation of burning heat in the mouth, the stomach, the intestines,
&c. and yet the mucous surface, the seat of this sensation, does not
disengage more caloric than usual; we may be convinced of this by
placing the fingers in the mouth. This sensation is of the same nature
as that which we refer to the glans penis when there is a stone in
the bladder, as that which is experienced at the end of the nose from
worms in the intestines, &c. There is no material cause of pain, and
yet there is suffering. Thus in intermittent fevers we experience a
cutaneous shivering, though the skin may be as warm as usual; I would
observe in respect to this, that the mucous membranes are hardly ever
the seat of an analogous sensation of sympathetic cold, but it is
almost always a sensation of heat that the aberrations of the vital
forces produce in them. Whence arises this difference between them and
the cutaneous organs? I know not. I attribute also to a sympathy of
animal sensibility the great thirst which takes place in all the severe
affections of any part. In all great wounds, after severe operations,
in experiments on living animals, &c. we observe this thirst which
depends upon a sympathetic affection of the whole mucous surface that
extends into the mouth, the stomach and the œsophagus.

Animal contractility cannot be put sympathetically into action in the
mucous system, since it does not exist in it.

The same is true of the sensible organic contractility. It is possible
that sometimes the kind of motion we have noticed, and which resembles
this property, may be sympathetically excited; I know no example of it.

The insensible organic contractility is here very frequently in
sympathetic activity. It is the skin especially which exercises by
means of this property, a great influence upon the mucous system. 1st.
In hemorrhages of the mucous surface of the womb, the nostrils, &c.
a cold body applied to the skin in the neighbourhood, contracts this
surface and stops the blood. 2d. Who does not know that the production
of most catarrhs is often the sudden consequence of the action of
cold on the cutaneous organ? 3d. In various affections of the mucous
membranes, baths which relax and expand the skin, frequently produce
happy effects. 4th. When the temperature of the atmosphere benumbs
the cutaneous tone, that of the mucous system receives a remarkable
increase of energy. Hence why in winter and in cold climates, in
which the functions of the skin are very much diminished, all those of
this system increase in proportion. Hence the more evident pulmonary
exhalation, the more abundant internal secretions, a more active
digestion, more quickly performed and consequently an appetite more
easily excited. 5th. When on the contrary the heat of the climate
and the season relax and expand the cutaneous surface, the mucous
surface is in proportion contracted; in summer, at noon, &c. there
is a diminution of the secretions, of that of the urine especially,
a slowness in the digestive phenomena from a defect in the action of
the stomach and intestines, an appetite slow to return, &c. 6th. In
various general affections of the skin, certain portions of the mucous
membranes are almost always affected. In scarlet fever, the throat
most usually suffers sympathetically. This phenomenon is very common
in small pox. 7th. In the latter periods of organic affections of the
viscera, as in phthisis, diseases of the heart, enlargements of the
liver, cancers of the womb, &c. the mucous membranes are affected like
the serous surfaces. The kind of atony in which they then are, produces
a more copious flow of mucous juices in them which are altered, become
more fluid, &c. hence the diarrhœas that are called colliquative,
which are then to the mucous surfaces, what dropsies are to the serous
ones; 8th. It is also to this atony that must be attributed the
pectoral hemorrhages which so frequently take place in the last periods
of organic diseases, in those of the heart especially. During the short
time that I have been at the Hôtel Dieu, there has already died more
than twenty patients whom I have opened, of these affections almost
forgotten by all practitioners before the time of Corvisart; I have
only observed four examples in which passive hemorrhage of the lungs
was not the precursor of death.


_Character of the Vital Properties._

From what we have thus far said, it is evident that the mucous system
is one of those of the whole economy, in which life is the most active.
Always in contact with substances that stimulate and irritate it, it is
as it were like the skin, in continual action. Yet the life is not the
same in all its parts; it undergoes in each remarkable modifications,
which no doubt depend on those we have pointed out in the organization
of this system, in the nature of its corion, in the arrangement of its
papillæ, in the distribution of its vessels and its nerves, in that of
its glands, &c. for as we have seen, none of these essential bases of
the mucous system is everywhere arranged in the same manner. There is
an organization common to the system, and one peculiar to each of its
divisions. It is the same in regard to its life; there is a life common
to the system, and as many peculiar ones as there are parts to which it
is extended. We know how much the animal sensibility of the pituitary
membrane differs from that of the palatine, how powerfully the membrane
of the glans penis and the urethra is stimulated by the passage of the
semen which makes no impression upon any other mucous surface. The same
is true in regard to the organic sensibility and the contractility of
the same species. Each mucous surface, in relation with the fluid it is
accustomed to, would bear the others with difficulty. The urine would
be a stimulant for the stomach and the gastric juice for the bladder;
the bile that remains in the gall-bladder would produce a catarrh upon
the membrane of the nose, in the vesiculæ seminales, &c.

From these varieties in the vital forces of each division of the
mucous system, it is not astonishing that the diseases of this system
should also be very variable. Each has a general character, but this
is modified in each mucous surface. There is an order of symptoms
common to all catarrhs; but each has its peculiar signs, each has
its different products. The fluid from a pulmonary catarrh does not
resemble that from a nasal one; that coming from a urethral, vesical
catarrh, &c. is wholly different from that from an intestinal one.
These fluids exhibit in their morbid changes the same differences that
we have pointed out in their natural composition, differences which are
derived like them, from the different vitality of each portion of the
mucous system.

It is to these varieties of life and the vital forces that must be
referred also those of the sympathies. Each portion of this system has
a peculiar sympathetic action upon the other organs. The pituitary
alone being irritated produces sneezing. You would excite in vain the
extremity of the glans penis, the rectum, &c. you would never produce
vomiting as you do by stimulating the uvula.

An important remark should here be made in regard to the stomach. We
know that there is no organ which performs a more important part in the
sympathies than this. The least affection of this important viscus,
the least gastric derangement, spread over the whole animal economy a
painful influence; all the other parts feel it. I do not believe even
that there is any uneasiness more fatiguing and general than that which
we then experience in certain cases. The general weakness which takes
place in hunger almost instantaneously, is sympathetic; the alteration
of nutrition has not had time to produce it. The same is true with
regard to the sudden increase of the forces which results from the
contact of the aliments upon the mucous surface of this viscus, an
increase which cannot be attributed to the passage of the chyle into
the blood, which has not yet had time to take place.

I think the stomach owes this important part in the sympathies
principally to its mucous surface. In fact, 1st, its serous surface has
no connexion with it, since it is there of the same nature as in all
the rest of the peritoneum, besides in what is called inflammation of
the abdomen, and in which this serous surface is especially affected,
we do not observe such numerous sympathetic relations. 2d. The fleshy
coat appears to be the same as that of the whole intestinal canal;
why then should it have different influences? 3d. As it respects
blood-vessels and nerves of the ganglions, the stomach is nearly
organized like the rest of the alimentary tube. 4th. It has besides the
par vagum; but is this nerve alone capable of producing such numerous
phenomena? It can contribute to them; but certainly the peculiar
modifications which it experiences in the mucous surface, the peculiar
nature of this membrane contribute also much to it. No membrane is
organized like that of the stomach. Though we do not see perfectly
at first view its organic differences, reflection is sufficient to
convince us of them; thus on the one hand no one separates so great
a quantity of fluid, and on the other none furnishes one of a nature
analogous to that of the gastric juice.


ARTICLE FOURTH.

DEVELOPMENT OF THE MUCOUS SYSTEM.


I. _State of the Mucous System in the First Age._

The development of the mucous system follows in general the laws of
that of the organs to which it belongs. Early in the gastric apparatus,
later in the pulmonary and that of generation, it seems in its growth
rather to obey the impulse it receives, than to give one to what
surrounds it, an arrangement common to almost all the systems which
contribute to form the different apparatus. Observe in fact that there
is always in the growth certain parts to which all the others refer;
thus in the cerebral apparatus, the early size of the brain produces
that of the bones of the cranium, of the dura-mater, the pia-mater,
the arachnoides and the vessels; thus it is on account of the spinal
marrow, that the vertebral canal is so evident in the fœtus; thus
all the serous surfaces have a growth in proportion to that of their
respective organs, &c. &c. I would remark however that the early growth
of the systems which are only to follow that of the parts to which they
are destined, is only in the dimensions of length, breadth, &c. The
thickness most commonly does not correspond with these dimensions. Thus
the bones of the cranium though broader in proportion than those of the
pelvis in the fœtus, are not thicker. The extent of the dura-mater is
in proportion greater than that of the albuginea which belongs to the
same system; but the organization is no further advanced.

In the fœtus, the delicacy of the mucous texture is extreme, the
papillæ are hardly perceptible. But by carrying the hand over a mucous
surface, we feel there an extremely delicate velvet and such as is not
equalled by the finest velvet. The redness of this system is not then
as evident, because no doubt less blood penetrates it, as the various
functions which are afterwards to take place upon these surfaces, as
digestion, the excretions, respiration, &c. are but feeble or entirely
wanting. At this age, the quantity of blood seems to be in an inverse
ratio in the skin and in these surfaces. The mucous red is then like
the muscular, of a very deep tinge, often even livid, on account of the
nature of the blood circulating in the arteries. Then the adhesions
of the mucous texture to the subjacent cellular are less; those
especially of this last with the surrounding parts are very slight;
thus it is very easy to draw out whole the internal portion of the
intestines of the fœtus, from the external covering that contains it,
so as to see two cylindrical canals, one of which is muscular and
serous, the other cellular and mucous. The stretching destroys in
this experiment all the valvulæ conniventes, and the small intestines
are as smooth on the interior as the large, in the canal artificially
extracted. If we subject this canal to ebullition, much more scum
arises from it than in the adult; this scum is white and never green.
The crisping that takes place a little before the first boiling,
diminishes more in proportion the length of the canal, and consequently
appears to be stronger.

At birth, when respiration and digestion suddenly commence, the
secretions increase, the mucous system acquires a remarkable degree of
activity. It is instantly excited powerfully by the many new substances
with which it is in contact. It is by it and by the cutaneous system
that bodies foreign to ours then immediately stimulate it, and so
much the more efficaciously, as the double surface which receives the
excitement is not accustomed to it. Then the red blood which penetrates
the mucous system, gives it an increase of energy and sensibility,
which renders it still more proper to receive impressions. Thus the
mucous juices which till then stagnated upon their respective surfaces,
without fatiguing and irritating them, are suddenly for them, on
account of their increase of sensibility, stimulants which excite them,
and force the subjacent muscles to contract. Then the urine becomes for
the bladder a cause that promotes the contraction of it. A few instants
after birth, all the openings in which the mucous membranes begin, open
and permit to escape the meconium, the urine and all the mucous juices.
This internal and general shock that empties all the mucous cavities,
renders them fit to become the seat of the great functions which are
soon to take place in them.

When all the internal functions are in activity, the mucous surfaces
experience no more sudden changes, analogous to that of which I have
spoken. They grow like the other viscera in a slow and insensible
manner; they preserve for a long time their original softness, which is
remarkable, especially in the nose, the stomach, &c. and which during
lactation, is not adapted in the infant, to the solid substances with
which the adult is nourished. Is this softness the cause of the mucous
affections which are in general so common at that age? We know that
then the mucous juices abound; the pituitary membrane is more moist;
the stomach and intestines are frequently affected with a species of
catarrh which is the cause of the looseness that we have so often to
combat in infancy. The membrane of the bronchia is also frequently
diseased. The two extreme ages of life resemble each other by the
abundance of the mucous juices secreted upon their respective mucous
surfaces.

In youth the mucous system is in very powerful action. The active
hemorrhages of this system are very frequent at this age; those of
the nose, the bronchia and even the stomach often take place; those
of the portions of this system, subjacent to the diaphragm, are then
less common. Observe that in man, hemorrhages of the gastro-pulmonary
surface are infinitely more frequent than those of the genito-urinary
surface, which on the contrary, are much more numerous in woman in whom
one of them is natural to a part of this surface, viz. menstruation.

At the period of puberty, the development of the genital parts in both
sexes, gives much activity to a part of the genito-urinary surface;
then menstruation begins upon that of the womb; then the sensibility
of the urethra is raised in order to feel acutely the passage of the
semen. Observe that this increase of energy is not attended with a
weakness of the other parts, as happens in many cases; on the contrary,
all the systems, all the apparatus seem to borrow, from the force which
the genital parts acquire, an increase of action.


II. _State of the Mucous System in the subsequent Ages._

In the years which succeed youth, the mucous system continues to grow,
thicken and become firmer. Its vital energy seems still to predominate
for some time, in the superior surfaces, as in the pituitary, the
membrane of the bronchia, &c. thus the affections of these parts are
more frequent until the thirtieth year. But as we advance in age, the
abdominal mucous surfaces appear to predominate over the others, as in
general all the organs of this region do.

Besides, a thousand causes in the course of life, make the state of
the mucous system vary. We do not find it in two subjects, with the
same shade of colour, with the same density, with the same external
appearance. By taking any surface upon many subjects, that of the
stomach, for example, we easily see these differences, with which we
must be struck if we have opened dead bodies but ever so little.

The redness of the mucous texture is very bright until the thirtieth
year; after that, it begins to alter. This texture becomes more and
more pale in old age; the blood enters it but in small quantity; it
acquires more consistence and density. The fingers carried over it
no longer perceive that softness, that velvet so remarkable in the
first age. Its forces, which grow languid, render difficult, in the
excretories, the exit of the fluids which pass through these tubes to
be thrown out. Yet the mucous glands still secrete their fluids in very
great abundance. Often even these fluids increase in proportion which
constitutes the catarrhal affections, so common in old age. But these
affections then have the same character as the functions of the whole
system; secretion takes place slowly; the disease is always chronic;
most often it terminates only with life.

The mucous absorption is, at this age, slow and difficult, like all the
others; the various contagions are taken much less easily, either by
the respiratory surfaces, or by the contact of contagious miasmata upon
the neighbouring surfaces of the skin. The chyle slowly absorbed, makes
the digestive periods longer.




SEROUS SYSTEM.


This system, the name of which I borrow, like that of the preceding,
from the fluid that constantly lubricates one of its surfaces, is
always like it arranged in the form of membranes, and never in
fasciculi like the muscular system, or in round bodies like the
glandular. It is formed by the peritoneum, the pleura, the pericardium,
the arachnoides, the tunica vaginalis, &c. The term serous membrane
will then be very often used to designate it. No one, I believe, before
the publication of my Treatise on the Membranes, had considered in a
general manner these organs, which perform a less important part in
the functions than the mucous, but which in diseases are almost as
frequently affected. Pinel, who has perceived the analogy of their
inflammations, has taken this system as a character of one of the
classes of his phlegmasiæ.


ARTICLE FIRST.

OF THE EXTENT, FORMS, AND FLUIDS OF THE SEROUS SYSTEM.

The serous system occupies the exterior of most of the organs of which
the mucous lines the interior; such are the stomach, the intestines,
the bladder, the lungs, &c. We see it around all those that are
essential to life, as around the brain, the heart, all the gastric
viscera, the testicles, the bladder, &c. It does not form, like the
mucous system, a surface everywhere continuous upon the numerous
organs on which it is spread. But it is always found insulated in its
different divisions which never have any communication. The number of
these divisions is somewhat considerable. By considering in one view
all the different serous surfaces, we see that as a whole they exceed
the mucous surfaces viewed also in a general manner. One consideration
is sufficient to convince us of it. The mucous and serous surfaces
accompany each other in a very great number of parts, as in the
stomach, the intestines, the lungs, the bladder, the gall-bladder, &c.
so as to exhibit in them nearly the same extent. But on the one hand,
the mucous surfaces extend where the serous are not met with, as in the
nasal fossæ, the œsophagus, the mouth, &c. &c. and on the other, there
is a very great number of serous surfaces existing separately from the
mucous, as the pericardium, the arachnoides, &c. Now if we compare
the extent of the separate serous surfaces, with that of the separate
mucous surfaces, we shall see that the first is much greater than the
other.

These considerations, apparently minute, deserve however particular
attention, on account of the relation of functions existing between
these two surfaces taken as a whole, a relation which is especially
connected with the exhalation of the albuminous fluids produced by one,
and with the secretion of the mucous fluids, of which the other is
the seat. Besides, in examining the extent of each serous membrane in
particular, we see great varieties from the peritoneum which has the
greatest surface, to the tunica vaginalis which has the least.

The serous surface taken as a whole, compared with the cutaneous
surface, is also evidently superior to it in extent; so that in this
respect, the quantity of albuminous fluids constantly exhaled within,
appears to be much more considerable than that of the fluid which is
incessantly thrown off by insensible transpiration; I say in this
respect, for different circumstances, by increasing the action of the
cutaneous organ, can re-establish the equilibrium in the exhalation
of these two fluids, one of which re-enters by absorption into the
circulation, and the other is wholly excrementitious. I do not know
even if the pulmonary and cutaneous exhalations united are not less
than those which take place upon the serous surfaces.

Every serous membrane represents a sac without an opening, spread upon
the respective organs that it embraces, and which are sometimes very
numerous, as in the case of the peritoneum, sometimes single, as in the
case of the pericardium, covering these organs so that they are not
contained in its cavity, and so that if it was possible to dissect them
from their surface, we should have this cavity whole. This sac has in
this respect the same arrangement as those night caps, which are folded
within themselves; a trifling comparison, but which gives an accurate
idea of this sort of membranes.

From this general arrangement, it is easy to understand that the
serous membranes are never opened to permit the vessels and nerves to
penetrate the respective organs to which they go or from which they
come off, but that they always wind round them and accompany them
to the organ, and thus form for them a sheath which prevents them
from being contained in their cavities; this removes the danger of
infiltration of serum which lubricates them, an infiltration which
would take place through the neighbouring cellular texture, especially
if they were dropsical; if, as in the fibrous membranes, they were
pierced with foramina for the passage of these vessels and nerves.
This arrangement, exclusively remarkable in the membranes of which we
are treating, and in the synovial ones, is evident at the entrance
of the vessels of the lungs, the spleen, the intestines, the stomach,
the testicles, &c. We see it very well in the arachnoides, a membrane
essentially serous, as I have demonstrated elsewhere.

From the general idea that we have given of these membranes, it is
also easy to understand how almost all are composed of two distinct
parts, though continuous, and embracing, the one the internal surface
of the cavity where they are found, the other the organs of this
cavity; thus there is a costal and pulmonary pleura, a cranial and
cerebral arachnoides, one portion of peritoneum spread upon the gastric
organs, and another upon the abdominal parietes, a free portion of the
pericardium, and one adhering to the heart. The same arrangement exists
in the testicles, &c.

Though the serous membranes may be separate, yet there sometimes
exists communications between them; that for example of the cavity of
the omentum with that of the peritoneum, that of the cavity of the
arachnoides with the cavity of the membrane which lines the ventricles
by the canal that I have discovered, and the external orifice of which
is seen below and at the posterior part of the corpus callosum; whilst
the internal one is seen above the pineal gland, between the two rows
of small round bodies which are usually found in this place.

There is but one example of continuity between the serous and mucous
membranes, that which exists, by means of the Fallopian tube, between
the peritoneum and the uterine surface. How does the respective nature
of the two membranes change here?


_Free Surface of the Serous Membranes._

Every serous membrane has one of its two surfaces free, everywhere
contiguous to itself, and the other adhering to the neighbouring
organs. The first is remarkable for its polish, which especially
distinguishes this system and the following, from all the other
membranes. All the organs which exhibit this arrangement owe it to the
covering they borrow from it. The liver ceases to be smooth and shining
at its diaphragmatic edge where the peritoneum abandons it. There is
in this respect a great difference in the appearance of the anterior
and posterior face of the cæcum. The bladder is rough wherever the
peritoneal covering is wanting. The cartilages of the ribs have not the
polish of those of the articulations which the synovial membrane covers.

Does this remarkable attribute of the serous membranes depend on the
compression exerted upon them? Their situation in places where they
are exposed to continual friction, would seem to make it probable.
Bordeu thought so, when he said that all the parts of the abdomen
are originally covered with cellular texture, which by pressure is
afterwards changed into membranes; so that the peritoneum is formed
partially upon each gastric organ, and its different parts give birth,
by uniting, to the general membrane. This explanation of the formation
of the peritoneum is applicable, according to him, to the pleura,
the pericardium, and all the analogous membranes. But if this is the
progress of nature, 1st, why, whatever be the period at which we
examine the fœtus, do we find the peritoneum and the serous membranes
as much developed in proportion, as their corresponding organs? 2d.
How are the numerous folds of these membranes formed, such as the
mesentery, the omentum, &c.? 3d. Why are there parts where they do not
exist though they are exposed to as great friction as that of the parts
where they are found? Why, for example, are the sides of the bladder
destitute of it, whilst it covers its superior part? 4th. Why does it
not also form serous surfaces around the great vessels of the arm, the
thigh, &c. which impart to the neighbouring organs an evident motion?
5th. Why does not the thickness of the serous membranes increase
where the motion is strongest and diminish where it is weakest? Why
for example does the thickness of the tunica vaginalis equal that of
the pericardium? 6th. How can friction internally produce an organized
body, whilst externally it constantly disorganizes the epidermis? 7th.
How can we associate the vascular lymphatic texture of the serous
membranes with the pressure that produces them? The impossibility of
resolving these numerous questions proves, that it is not to mechanical
pressure that must be attributed the formation of the serous membranes
and the polish of their surface; that their mode of origin is the same
as that of the other organs; that they commence and are developed with
them; that this polish is an evident result of their organization, as
the mucous papillæ depend upon the texture of the surfaces to which
they belong. What would be said of a system in which these papillæ
should be attributed to the pressure of the aliments upon the stomach,
of the urine on the bladder, the air on the pituitary membrane, &c.?

The free surface of the serous membranes separates entirely from the
neighbouring organs those upon which these membranes are spread; so
that they are to these organs real boundaries, barriers, if I may use
the term, or integuments, if it should be preferred, very different
however from those which are external. Observe in fact that all the
principal viscera, the heart, the lungs, the brain, the gastric
viscera, the testicles, &c. limited by their serous covering, suspended
in the middle of the sac that it forms, only communicate with the
adjacent parts where their vessels enter; everywhere else there is
contiguity and not continuity.

This insulation of position coincides very well with the insulation of
vitality which is remarked in all the organs, and especially in those
that we have just noticed. Each has its peculiar life, which is the
result of a particular modification of its vital forces, a modification
which necessarily establishes one in the circulation, nutrition and
temperature. No part feels, is moved and nourished like another, unless
it belongs to the same system. Each organ executes on a small scale the
phenomena which take place on a large one in the economy; each takes
from the circulation the aliment that is proper for it, digests it,
throws back into the mass of blood, the portion which is heterogeneous
to it, and appropriates to itself that which can nourish it; it is
digestion in miniature. No doubt the ancients wished to give an idea of
this truth which has been so well explained by Bordeu, when they said
that the womb was a living animal within another. A very important use
then of the serous membranes is to contribute, by rendering independent
the position of their respective organs, to the independence of the
vital forces, life and functions of these organs.

Let us not forget to consider under the same point of view, the moist
atmosphere with which they are constantly surrounded, an atmosphere
analogous to that which the cellular texture forms for various other
organs. In this atmosphere all the morbific emanations of the organ go
and are lost, if we may so say, without these emanations injuring the
other organs. We have seen that this atmosphere in the cellular system
is sometimes the seat of phenomena wholly different, and serves to
transmit diseases from one organ to another. Now the serous membranes
are a barrier much less easily surmounted, because they have not
filaments which go from one organ to another, there is only contiguity
as I have said, with the organs that they surround. We very rarely see
in the abdomen a disease of the liver communicated to the intestines,
one of the spleen passing to the stomach, &c.

The smoothness of the free surface of the serous system greatly
facilitates the motions of the organs which it covers. We have already
observed that nature employs two principal means for this object, viz.
the membranes and the cellular texture. By distributing externally
the second of these means, it has designed the first especially for
internal motions. The smoothness and moisture of the serous surfaces
are singularly favourable for them. These internal motions are usually
regarded only in an insulated manner, as relating to the functions of
the organ that executes them, as in relation to the circulation for
the heart, respiration for the lungs, digestion for the stomach, &c.
But they should also be considered in a general manner; they should be
regarded as carrying through the whole machine a continual excitement
which supports and animates the forces and the action of all the organs
of the head, the chest and the abdomen, which receive less sensibly
than the organs of the extremities, the influence of external motions.
It is these internal motions that excite, sustain, and develop within,
the nutritive phenomena, as the motions of the thigh, the arm, &c.
without, favour the nutrition of the muscles which are found there;
this is seen very evidently in bakers and other mechanics who exert
more particularly this or that part. It is thus that the serous
membranes contribute indirectly to the nutrition and growth of their
respective viscera; but they never have a direct influence upon this
nutrition, because their organization and life are different from the
life and organization of these viscera.

The free surface of the serous system differs essentially from that of
the mucous, in this, that it contracts frequent adhesions. The pleura
is of all the serous organs, that in which these adhesions are the most
evident. We find almost as many dead bodies in which they exist, as we
do those in which they do not. Next to the pleura is the peritoneum,
then the pericardium, then the tunica vaginalis, then the arachnoides,
which is that of all the serous surfaces in which adhesions are the
least frequent, though I have observed them in it. These adhesions
exhibit many varieties which can be studied best on the pleura, which
are as follows.

1st. Sometimes the costal and pulmonary portion are so identified at
many points or in every part, that they make but a single membrane, and
are united as closely as the two edges of the lip in a hare-lip that
has been operated upon with success. 2d. At other times the adhesion
is so slight, that the least effort is sufficient to destroy it. I
have many times noticed this fact in the pericardium. I saw it once in
the tunica vaginalis of a man who had been operated upon for hydrocele
by means of injection, at the time I was surgeon for operations at
the Hôtel Dieu. Separated then from each other, the two surfaces were
uneven; they lost their polish. 3d. Frequently between the costal
and pulmonary portion of the pleura, between the surfaces of the
peritoneum, &c. there are several elongations of various lengths, which
form a kind of loose bridles, traversing the serous cavity, having the
same organization and polish as the membrane of which they appear a
kind of fold, containing in their interior a species of small canal,
because they are formed by two layers united together, resembling
very much the elongation of the synovial membrane of the knee, which
goes from the posterior part of the patella to the space between the
condyles of the femur, having also an appearance analogous to the
different natural folds of the peritoneum. We can hardly conceive that
these filaments so regularly organized can result from inflammation. I
am inclined to believe that they are owing to an original conformation.
4th. Frequently between the two portions of the pleura, there are seen
many other elongations wholly different, which are not smooth, and do
not form canals, but which appear to be flocculent and really analogous
to the cellular layers; so that where they exist it may be said, that
the membrane is entirely changed into this texture, which is besides,
as we shall see, the essential base of its organization. 5th. I do
not speak of the adhesions produced by false membranes, by albuminous
flakes, intermediate to the two portions of a serous surface, &c. These
adhesions are to a certain point foreign to these surfaces.


II. _Adherent Surface of the Serous System._

The external surface of the serous membranes adheres almost everywhere
to the neighbouring organs; it is rare in fact to see these membranes
detached on both sides. The arachnoides at the basis of the cranium,
and some other examples are exceptions. This adhesion of the serous
membranes to their respective organs, is wholly different from that
of the fibrous membranes. In this last, the passage of the vessels so
unites the two parts, that their organization, seems to be common,
and when one is removed, the other almost always dies, as is seen in
the periosteum in relation to the bones, &c. On the contrary, every
serous membrane is almost foreign to the organ it surrounds; their
organization is different. The following are proofs of it;

1st. We very often see these membranes abandon and cover again
successively their respective organs; thus the broad ligaments, at a
great distance from the womb in the ordinary state, are to it like a
serous membrane during pregnancy. An intestine when distended borrows
from the mesentery a covering that quits it when it contracts. The
omentum is by turns, as Chaussier has well observed, a loose membrane
in the abdomen and a covering of the stomach. The peritoneal envelope
of the bladder often leaves it almost entirely. Has not the hernial sac
of those enormous tumours of gastric viscera originally served to line
the parietes of the abdomen? Now it is evident, since the different
organs can exist separate from their serous membranes, that there is
no connexion between their organization. 2d. It is always a loose
texture, easily stretched in every direction, that serves as a means of
union, and never a sanguineous vascular system, as in most of the other
adhesions. 3d. The affection of an organ is not a necessary consequence
of that of its serous membrane, and reciprocally the organ is often
affected and the membrane does not become diseased. For example, in the
operation for hydrocele, the testicle remains almost always sound in
the midst of the inflammation of its tunica vaginalis. The inflammation
of the mucous membrane of the intestines is not a consequence of that
of their peritoneal covering; and reciprocally in the various acute
catarrhal affections of the organs with a mucous membrane within and
a serous one without, this last is never found inflamed. In a word,
the affections of the mucous membranes are everywhere very distinct
from those of the serous, though most commonly both contribute to the
formation of the same organ. It is evident that a line of demarcation
so great in the affections supposes one of course in the organization.
The life of the serous membranes then is entirely distinct from that of
their corresponding organs.

Yet there are cases where these membranes do not present this loose
adhesion, and where they become so united to the organs which they
line, that frequently the most delicate scalpel cannot separate them.
Observe the tunica vaginalis on the albuginea, the arachnoides on the
dura-mater, and other membranes which form what I have called the
sero-fibrous, &c. such is the connexion of these different surfaces,
that many have been mistaken to the present time for a single membrane.
There is however no more identity in the organization, than where the
serous membranes are more loosely attached to their respective organs,
as is seen in the peritoneum, the pleura, &c. Diseases sometimes
make this difference very evident. I have seen the arachnoides in a
subject that had been affected with a chronic inflammation, evidently
thickened on the internal surface of the dura-mater, without this
having experienced the slightest alteration; it was detached without
difficulty and torn with great ease.


III. _Serous Fluids._

Every serous membrane is moistened on its internal surface by a fluid
almost the same as the serum of the blood. The exhaling orifices
constantly pour it out and it is constantly taken up by the absorbents.
Its quantity varies. A mere dew in the natural state, it is exhaled
in vapour when the serous surfaces are laid bare and allow the air to
dissolve it. It is in general more abundant in dead bodies than in
the living, because on the one hand the transudation which the tonic
forces prevent, then easily takes place from the destruction of these
forces, and supplies the place of the vital exhalation, by transmitting
mechanically by their weight, the fluids of the surrounding organs to
the different serous cavities, and because on the other hand, this
destruction of the tonic forces prevents every kind of absorption;
hence the stagnation and accumulation of this fluid. We know to what an
extent this increases in various dropsies, especially in that of the
abdomen.

Does this quantity vary according to the different states of the
organs which the serous membranes cover? It has been long said, that
the synovia is exhaled in greater abundance in the motion of the
articulations, than in their state of rest. I have no data on this
point founded upon experiment; but I am certain that I have many times
observed in living animals, that the exhalation of the serous surface
of the abdomen does not increase during digestion, or at least if it is
greater, absorption becomes more active, and thus the surface of the
peritoneum is not more moist than at another time. I have opened the
thorax of many small guinea-pigs, after having first made them run
a long time in the chamber in order to accelerate their respiration,
and I have not observed greater moisture on the pleura. Yet it cannot
be doubted, as we shall see, that the quantity of the serous fluids
may be very variable in the different acute diseases; that the serous
membranes exhale more or less of them, according to the manner in which
they are sympathetically affected.

In the first periods of inflammations, in which the exhalants of the
serous membranes are full of blood which is preternaturally introduced
into them, the serum does not ooze in greater quantity from their
free surface. Then as they are on the one hand very sensible, and
very dry on the other, the motions of the organs that they cover are
wonderfully painful. It is in these first periods that adhesions take
place. If they are not formed either on account of the motion, or for
other reasons, and if resolution of the inflammation does not take
place, then happens to the serous surfaces what happens to a wound not
united; they suppurate, but this suppuration is never attended with
ulceration or erosion of their substance. However abundant the purulent
collections may be, these membranes always remain sound; their texture
is only more or less thickened; pus is thrown out by them, like the
natural serous fluids, that is by exhalation. We know how much this
fluid varies in consistence from milky serum, to the thickest false
membrane that adheres strongly to the surface that has exhaled the
materials of it.

The nature of the fluids of the serous system is very evidently
albuminous. The instant one of the membranes of this system is
plunged into boiling water, I have observed that it is covered with a
white layer which is concrete albumen, and which being removed some
time after, leaves the surface nearly of its original colour. All
the substances which coagulate albumen produce a similar layer upon
the serous surfaces. The experiments of Hewson, who has collected
some spoonsful of these fluids in the great animals, confirm their
albuminous nature. Rouelle and Fourcroy who have analyzed the water
of dropsies have also found albumen predominant in it. Observe upon
this subject that all the white flakes swimming in this water, that
the false membranes that form in it and the white fluids which give it
the appearance of milk, appear to be only albumen which is found in
different degrees of consistence. It might be said that the heat of
inflammation has produced the same phenomenon during life, that common
caloric does upon the white of an egg, the water of dropsies, &c. I
shall not treat of the other accessory principles that enter into the
composition of the serous fluids.


ARTICLE SECOND.

ORGANIZATION OF THE SEROUS SYSTEM.

The first characters of the structure of these membranes are a white,
shining colour, less brilliant than that of the aponeuroses; a variable
thickness, very evident upon the liver, the heart, the intestines,
&c. hardly discoverable upon the arachnoides, the omentum, &c. a
remarkable transparency whenever these membranes are raised for a
considerable extent, or are examined where they are detached on both
sides, as on the omentum.

All have but a single layer which it is possible, at the places where
it is thick, to raise from the cellular layers, but which can never
be neatly divided into two or three portions; a character essentially
distinct from those of the mucous membranes. The action of a blister
on their external surface first laid bare, for example, on a portion
of intestine drawn out in a living animal, does not make a pellicle
rise upon it, as upon the skin, a pellicle under which the serum is
collected. I have frequently made this attempt. What is the immediate
structure of this single layer of the serous membranes? I shall now
examine it.


I. _Cellular Nature of the Serous Texture._

Every system is in general, as we have thus far seen, an assemblage,
1st. of common parts, which are especially the cellular texture, the
blood vessels, the exhalants, the absorbents and the nerves, which
form as we have said the outline and the frame of it, if I may so
express myself; 2d. of a peculiar fibre formed by a substance which
is deposited in this outline, by gelatine, for example, for the
cartilages, by gelatine and phosphate of lime for the bones, by fibrin
for the muscles, &c. That which makes these organs resemble each other
then is the cellular organ, the vessels and the nerves; that which
distinguishes them, is their peculiar texture, which depends itself
upon a peculiar nutritive matter. A bone would become a muscle, if,
without changing its texture at all, nature had imparted to it the
faculty of secreting fibrin, and of encrusting itself with it, instead
of separating the phosphate of lime and being penetrated with it. But
the serous system does not appear to have in it a distinct nutritive
matter, and consequently a peculiar texture. It is only formed of the
mould, the outline of others, and is not penetrated by a substance
that characterizes it. Almost wholly cellular, it does not differ from
this system in its common form, except by a degree of condensation, by
an approximation and union of cells which are found scattered in the
ordinary state.

The following are the proofs that the texture of the serous system is
wholly cellular. 1st. There is an identity of nature where there is
an identity of functions and diseases; now it is evident that the uses
of these membranes and of the cellular texture, as it respects the
continual absorption and exhalation of lymph are completely the same,
and that the phenomena of the various dropsies are common to them,
with the difference only of the effusion in the one and infiltration
in the other. 2d. The inflation of air into the texture subjacent to
these membranes terminates by bringing them almost to a cellular state,
when it succeeds and is pushed for some time; an experiment which is
frequently very difficult. 3d. Maceration, as has been remarked by
Haller, produces at length the same effect, but in a still more evident
manner. 4th. The various cysts, hydatids, &c. whose appearance, texture
and nature even are entirely the same as in the serous membranes, as we
have seen, always arise in the midst of the cellular texture, grow at
its expense and are wholly formed of it. 5th. No fibre is found in the
serous membranes; a character that distinguishes it from all the other
organs and analogous to that of the cellular texture.

To these various proofs of analogy, of identity even of the cellular
and serous systems, we can add the action of different reagents, which
give results precisely similar in both. 1st. Every serous membrane
when dried, becomes transparent, does not turn yellow like the fibrous
and the mucous membranes, preserves a pliability foreign to these
membranes when dried, and gradually resumes its original state when it
is immersed in water. 2d. It becomes putrid much slower than the mucous
surfaces, the muscular layers, the glands, &c. This is remarkable in
the abdomen, upon the peritoneum which is frequently almost untouched,
when every thing is putrid around it, as may be seen by removing it;
for its transparency would make you believe at first view that it was
altered, if you examine it upon the fleshy and mucous surfaces. 3d.
Maceration at the ordinary temperature of cellars, reduces with great
difficulty to a pulp the serous membranes. The omentum, the finest
and most delicate of these membranes has resisted it for a very long
time in my experiments. This phenomenon is particularly striking when
compared with the maceration of tendons which are so resisting, and
which support such great efforts during life. These become pulpy in
water before the omentum is touched. The same phenomenon takes place
with regard to all the other serous surfaces. 4th. In boiling water,
these surfaces acquire the horny hardness like the fibrous system,
but furnish infinitely less gelatine; they do not become yellow like
it. The pleura in those portions of the thorax of animals that are
brought to our tables, has almost its ordinary appearance; only it
is less shining, has lost the faculty of crisping from the action of
caloric, is no longer affected in the same way by acids, &c. If it was
of a fibrous nature it would have disappeared in gelatine, on account
of its delicacy. I shall say the same of the external membrane of the
spleen, the liver and the lungs. Compare these membranes, that are
brought to our tables, when boiled with the intermuscular aponeuroses,
the tendons, &c. you will see that it is impossible to confound, as has
been done, all the white textures together, in regard to their nature.

If we compare the different effects of agents the most known upon the
serous system, with those that we have observed upon the cellular
system, we shall see that they are entirely the same; that these two
systems are consequently analogous, and even identical.

The serous system when it putrefies in the open air does not become
green like the skin, but is of a dull and very deep grey. During life,
on the contrary, its blackness is very evident in gangrene which is
sometimes the result of an acute inflammation, sometimes of those
chronic inflammations, attended with many small white tubercles, which
are so frequently found upon these membranes. This difference arises
from the circumstance, that in the dead body these surfaces are not
penetrated with blood at the time they become putrid; whereas they
contain much during life, when putrefaction succeeds inflammation which
has filled the exhalants with it. Many other facts prove, that the
greater the quantity of blood there is in a part when it putrefies, the
more livid and black it becomes. In the many dead bodies that I have
opened, I have never yet observed gangrene except in the peritoneum.
I have never seen it in the pleura, the arachnoides, the pericardium,
the tunica vaginalis; it no doubt takes place in them; but I think I
have opened dead bodies enough to allow my observation to establish as
a general principle; that the peritoneum is more subject to it than all
the other analogous organs.

Though the different considerations offered above establish much
analogy between the cellular and the serous systems, they exhibit
however real differences. First their external appearance is not
the same. Then there is something in their intimate nature that we
are unacquainted with, and which differs also; for whenever two
organs are identical in their nature, they are subject to the same
affections; now there is a disease of the serous surfaces that is not
seen in the cellular system; it is those slow inflammations of which
I spoke just now, a disease which should not be ranked in the class
of the phlegmasiæ, and which the production of the small tubercles
that attend it, especially characterizes. Authors who have not
sufficiently attended to it, have denominated it chronic enteritis in
the peritoneum, latent inflammation in the pleura, &c. though however
foreign to every subjacent organ, except in the latter periods when it
is propagated by the cellular texture, it has its seat exclusively in
the serous membranes, and is an affection peculiar to these membranes,
as miliary eruptions are to the cutaneous surfaces, as aphthæ to the
mucous surfaces, &c. Add to this difference that of the pus which the
cellular texture and the serous surfaces secrete; this fluid is not the
same in the two systems. The difference of its nature is not known; but
its external appearance is by no means the same.


II. _Parts common to the Organization of the Serous System. Exhalants._

A very evident exhalation is constantly going on upon the serous
surfaces. A particular order of vessels is the agent of this
exhalation, the matter of which is the fluid mentioned above. These
vessels are very distinctly demonstrated in this system; it is the
only one in which the eye of the anatomist can accurately trace them.
The following are the means of seeing them; 1st, in a living animal,
draw out an intestine from the abdomen; it will have a reddish tinge
owing to the vessels under the serous coat, and hardly at all to the
vessels in this coat itself. Irritate it, and reduce the intestine
after attaching a string to it, as in the operation of hernia where
there is gangrene, draw it out again at the end of six and thirty or
eight and forty hours; it will exhibit many reddish lines, running over
this serous surface, and showing in it plainly the exhalants which
were insensible in the natural state, on account of the transparency
of their fluids. 2d. Very fine injections cover in an instant all the
serous surfaces with an infinite number of lines of the colour of the
injected fluid, lines which are evidently exhalants full of this fluid.
3d. In these injections an extremely fine dew is made to ooze out upon
the smooth surface of the serous membranes, a dew which takes place
without rupture or transudation, and of which the exhalants are the
sources. 4th. If a serous surface is laid bare in a living animal, and
wiped dry, it is soon after covered with new serum, which the exhalants
furnish.


_Absorbents._

From the texture of the serous membranes, it is evident that the
lymphatic system enters essentially into their formation, and that
they are probably only a net-work of exhalants and absorbents; for we
have seen that the cellular organ is an assemblage of them. But this
assertion which analogy dictates is also supported by direct proofs.
1st. The fluid of the dropsies of the different cavities varies
in density and colour; now Mascagni has always observed that the
lymphatics in their neighbourhood contained a fluid exactly analogous.
2d. The same author has found in two dead bodies, with a sanguineous
effusion in the thorax, the absorbents of the lungs loaded with blood.
3d. In a man who had become emphysematous after having been poisoned,
these vessels were distended with air. 4th. Coloured fluids injected
into the abdomen or thorax are soon after found, it is said, in the
neighbouring lymphatics, with the same colour. I have often repeated
this experiment; the injected fluid has been soon absorbed, but not
the matter which coloured it; so that this matter, more condensed
after absorption, tinged the serous surface, the lymphatics being as
transparent as usual. It is necessary in general to choose the abdomen
for these experiments, because the absorbents being much exposed on
the liver, can be more easily examined there. This absorbent faculty
is preserved some time after death; but care should be taken, in
order to obtain then the effect more certainly, to keep the animal,
if a warm blooded one, in a bath of nearly its own temperature; I
have had frequent opportunities of being convinced of this truth, and
of observing with Cruickshank, that what Mascagni has said upon the
absorption of dead human bodies, fifteen, thirty, forty-eight hours
even after death, is at least very much exaggerated. 5th. The following
experiment I make every year to demonstrate the absorbents; I macerate
for five or six hours the heart of an ox in water; at the end of this
time, the serous membrane of this organ, which hardly allowed these
vessels to be perceived, appears to be covered with them. 6th. When the
serous membranes are inflamed, the subjacent lymphatics are distended,
like them, by the red globules of blood, &c. &c.

It appears then to be demonstrated, 1st, that the absorbents open by
an infinite number of orifices upon the serous membranes; 2d, that
their origins a thousand times intermixed with each other, and with the
orifices of the exhalants, contribute especially to form their texture;
3d, that the difficulty of distinguishing the absorbent and exhalant
pores is no reason for denying their existence, this difficulty arising
from their extreme delicacy and from the oblique direction in which
they open between the layers of these membranes; thus the obliquity
of the insertion of the duct of Warton, and of the ductus choledochus
even would render the inspection of them very difficult, though these
ducts were infinitely larger; 4th, that from this structure, the serous
membranes, always arranged as we have seen in the form of sacs without
an opening, should be regarded as great reservoirs between the exhalant
and absorbent systems, in which the lymph in going from one remains
some time before entering the other, in which it undoubtedly undergoes
various preparations of which we shall always be ignorant, because it
would be necessary to analyze it comparatively in these two orders
of vessels, which is almost impossible, at least for the first, and
finally in which it serves different uses relative to the organs around
which it forms a humid atmosphere.


_Blood Vessels._

Do blood vessels enter into the structure of the serous membranes?
These vessels are very numerous around them, as is seen in the
peritoneum, the pericardium, the pleura, &c. they wind upon their
external surface and ramify there. But I have always doubted whether
the greatest number of those which are thus contiguous to them, really
make a part of their texture, and I am even convinced of the contrary.
The following considerations support my opinion. 1st. When these
vessels are injected, they can be easily raised with a scalpel from the
external face of these membranes, without injuring their continuity,
which can never be done in the fibrous or mucous membranes. 2d. No
blood vessel is discoverable on these membranes which are free on
both faces. The arachnoides at the base of the cranium furnishes an
example of this. 3d. The vessels frequently change relations with these
membranes. I have proved above that when the omentum is applied to the
stomach when it is full, the vessels that are between its layers, do
not mount with it upon this viscus, on account of the great stomachic
coronary which opposes it. When dead bodies having large hernias are
injected, the vessels that wind in the ordinary state upon the surface
of the peritoneum which corresponds to the ring, are not seen extending
below upon the hernial sac. Certainly the vessels that are observed
in the broad ligaments of the womb, do not follow them in the great
displacements they undergo in pregnancy.

I think it then very probable that the serous membranes have but very
few blood vessels; what are called arteries of the peritoneum, the
pleura, &c. are but trunks winding on their external surface, capable
of abandoning it when they are displaced, being as it were foreign
to them, not entering immediately into their structure, to which the
absorbent, exhalant and cellular systems almost alone contribute. No
doubt communications exist between the arterial system and the serous
membranes, by means of the exhalants; but nothing precise is yet known
upon the nature, arrangement, and to a certain extent even, the
functions of these vessels.


III. _Varieties of Organization of the Serous System._

We have seen the mucous system exhibiting in each part where it is
found, numerous differences of structure and varying in each region
and in each organ. The serous system varies also, though less than the
preceding. 1st. Each membrane has its peculiar structure. Compare for
example, the arachnoides and the peritoneum; the one fine, delicate
and transparent, yields to the least effort, has no resistance, tears
almost as soon as it is touched, never remains whole at the base of
the cranium, where it is free, if the brain is raised ever so little,
and has, when pressed between the fingers, a remarkable softness. The
other, thicker and more compact, bears without breaking all the efforts
imparted to the abdominal viscera; it can be pulled with impunity. Its
texture is wholly different. 2d. The different portions of the serous
membranes have not the same organization; the omentum is for example
evidently dependant upon the peritoneum and yet it does not resemble
it. I have observed that the intestinal portion of this membrane is
much more delicate than its hepatic, mesenteric portions, &c. That
the half of the tunica vaginalis which lines the albuginea and is
identified with it, is certainly not the same as the half which is
free on the side of the dartos muscle. I cannot say precisely in what
these differences consist; but the external appearance is sufficient to
establish them.

Ought we then to be surprised, if all the serous surfaces are not
equally subject to the same diseases; if inflammation attacks them
with such different degrees of violence; if it takes place ten times
upon the pleura to once that it appears upon the arachnoides; if in
the pericardium, the tunica vaginalis and the peritoneum, it does not
exhibit the same symptoms; if dropsies vary also wonderfully in each;
if the slow inflammations attack them differently, &c.? The pericardium
is subject to an affection which I have seen upon no other serous
surface, and which is yet extremely frequent upon this; I refer to
the white layers, more or less broad, that are formed on its internal
surface, which would be thought at first view to belong to its texture,
which can however be raised from it leaving it sound. I do not know
whence these layers come; do they correspond to the false membranes of
the pleura?

Neither should we be surprised at what has been said of the varieties
which the same membrane exhibits in its diseases. Frequently the whole
of the peritoneum is diseased, and the omentum remains sound and vice
versa. The layers of which I have just spoken are seen upon the cardiac
portion, and not upon the free portion of the pericardium.

Observe however that all the diseases of this system have a common
character which is evidently derived from the analogy of organization.
This and the synovial are the only ones in which large serous
collections take place, in which slow and tubercular inflammations
are formed. The most of their modes of adhesion belong only to
the serous system. Inflammation has a peculiar and distinctive
character in it, of which all the serous membranes partake with some
modifications. The inflammation of the meninges had been classed among
the serous phlegmasias, from the analogy of the symptoms, before I
had demonstrated that the arachnoides, one of these meninges, belongs
essentially to the serous system. It is on account of this membrane,
and not on account of the dura-mater which is of a fibrous nature, that
phrenitis should be referred to the diaphanous membranes.


ARTICLE THIRD.

PROPERTIES OF THE SEROUS SYSTEM.


I. _Properties of Texture. Extensibility._

The serous membranes are endowed with an extensibility much more
limited, than the enormous dilatations of which they are capable in
certain cases, would at first lead us to believe. The mechanism of
their dilatation evidently proves it. This mechanism depends upon
three principal causes; 1st, upon the development of the folds that
they form, and this is the most powerful of the three causes. Hence
why the peritoneum, which of all the membranes of this class, is the
most exposed to dilatations, as from pregnancy, ascites and visceral
enlargements, more frequent there than elsewhere; hence, I say, why
the peritoneum exhibits so great a number of these folds, such as the
mesentery, the mesocolon, the mesorectum, the two omentums, the fatty
appendices, the fold of the cæcal appendix, the broad ligaments of
the womb, the posterior ones of the bladder, &c. &c. Hence why also
these folds are seen around organs subject to habitual alternations of
dilatation and contraction, as around the stomach, the intestines, the
womb and the bladder; very evident in the second state, but slightly
apparent in the first. 2d. The enlargement of the serous cavities
belongs to the displacements of which their membranes are capable. Thus
when the liver is considerably enlarged, its serous membrane increases
its extent in part at the expense of that of the diaphragm, which being
drawn is detached and applied upon the enlarged viscus. I have seen,
in an aneurism of the heart, the pericardium which had been able to
yield but very little, detached in part from the portion of the great
vessels which it covered. 3d. Finally, the texture of these membranes
undergoes a real distension and elongation. But it is in general the
least sensible cause of the enlargement of their cavity; it is only
in the great enlargements that it has an evident influence; in common
cases, the two first causes are almost always sufficient.

I will make an important remark upon the subject of the displacements
of which the serous membranes are the seat in the motions of their
respective organs; it is that these displacements are very painful when
these membranes are inflamed. When the dilated intestines separate the
two diseased layers of the mesentery to lie between them, when the
stomach goes between those of the omentum, &c. when the peritoneum
is inflamed, the patient suffers much. Hence why flatulence is then
so painful, why it is then necessary to avoid taking at once a great
quantity of drink. We know the acute pain that a long inspiration
produces in pleurisy; it is because the lungs then dilate the pleura,
and tend to go between the folds which accompany the great pulmonary
vessels.


_Contractility._

It corresponds with the extensibility; it is less consequently than it
at first appears to be. When the peritoneum for example is contracted,
its different folds are formed; it returns to its place after having
experienced locomotions. But it cannot be denied that in great
dilatations these two properties are very sensible; for example, in
hydrocele as the water is evacuated, the tunica vaginalis evidently
contracts. The peritoneum after the paracentesis of the abdomen
exhibits the same phenomenon. At the time of performing the operation
of empyema, the pleura does not experience it so sensibly, not from
defect of contractility, but because on the one hand it adheres to the
ribs which do not contract, and on the other if the effusion is of
long standing, the lungs are so flattened by the pressure, that the
air can no longer dilate them, so that there remains a space between
the costal and pulmonary portion, which is filled with air. A similar
space would also remain at the moment of the operation, if the serum of
hydrocephalus was evacuated.

After long distensions, the serous membranes no longer contract;
the tunica vaginalis remains flaccid after frequent punctures, the
peritoneum after frequent pregnancies, &c. &c.


II. _Vital Properties._

The serous surfaces, being removed from the action of external bodies,
do not enjoy in the natural state the properties which put the living
organs in relation with external bodies; they have neither animal
sensibility nor contractility. Thus they would be very improper for
external integuments, or for linings of the organs which the mucous
membranes cover; they would give in fact no other sensation than
that of an obscure and indistinct feeling. They answer very well for
envelopes, integuments for internal organs, but not for sensible
envelopes. We have a proof of it in living animals in whom we can
irritate these membranes with impunity. I have many times seen dogs
in whom I had left the spleen drawn out of the abdomen, in order to
observe the phenomena arising from it, tear this organ without being
in a state of fury, eat it even and be thus nourished by their own
substance. They also often tear without pain the exterior of their
intestines when in experiments these are drawn out, and the animals are
left some time to themselves.

When external bodies are in contact with the serous system, they change
its natural state; they inflame it, as we see in the peritoneum, in the
tunica vaginalis laid bare, as we observe also always when a foreign
body introduced into the system acts upon them. Surgeons, as we know,
even employ this means to which they would in vain have recourse in the
mucous membranes, in order to procure artificial adhesions between the
parietes of these membranes. The different morbid irritations inflame
much more frequently the serous surfaces which in this state acquire
a very acute sensibility, greater even than that of the integuments;
so that these inflamed surfaces would be equally improper to serve for
integuments, because external bodies would excite them painfully.

The sensible organic contractility is nothing in the serous system; but
the insensible and the corresponding sensibility are kept in permanent
exercise in it, 1st, by the continual exhalation and absorption that
are going on there; 2d, by nutrition. These two properties are then
those which predominate in this system; thus upon their alterations
all its diseases turn. Acute inflammations, chronic inflammations with
tubercles, adhesions, dropsies, exhalations of pus, of milky serum, &c.
&c. are all derived from an excess, a defect or an alteration of these
two properties of the serous system. It is then also almost exclusively
that sympathies are put into action in it; so that the serous membranes
diseased either idiopathically or sympathetically exhibit always a
series of phenomena all of which suppose an increased internal motion,
or loss of tone in the exhalant and absorbent capillaries, and in the
peculiar texture of those membranes; whilst in the animal muscular, the
organic muscular systems, &c. these predominant affections which are
marked by convulsions and paralysis in one, and by irregular motions of
irritability in the other, do not suppose this internal alteration of
the texture of the diseased organ. Hence why these two last systems,
though frequently disturbed during life, exhibit but few changes
after death, whilst the serous system is a vast field for the morbid
anatomist.


_Sympathies._

The serous surfaces are capable of being influenced by the affections
of the other organs; this is very evident in the organic diseases of
the heart, the lungs, the liver, the spleen, the stomach, the womb,
&c. organs, which without having any known connexion of functions
with the serous surfaces, influence them however so that all their
morbid defects of organization are accompanied, in the latter periods,
by different serous collections in the great cavities, collections
evidently owing to a derangement of the organs which constantly exhale
this fluid. I shall make upon this point two observations; the first
is that the serous surfaces nearest the diseased organ, are in general
the most susceptible of being influenced by it. Thus in the diseases of
the heart and the lungs, the serous collections take place especially
in the thorax, whilst ascites is always the first consequence of
enlargements of the liver, the spleen, &c. the pleura and the
pericardium being filled subsequently. We know that most sarcoceles
are complicated with dropsies of the tunica vaginalis; whence results
hydro-sarcocele, a disease which surgeons consider separately, but
which is the same as those of the preceding cases, which might in
this respect be called hydro-phthisis, chronic hydro-hepatitis,
hydro-carcinoma of the womb, &c.

The second observation that I have to make is, that whenever the serum
is thus collected in the cavities, in consequence of an organic disease
of a viscus foreign to the membrane, this serum is limpid, transparent,
and probably of the same nature as that which circulates in the
lymphatic vessels. The exhalants which form it not being then in fact
diseased, their action not being increased or that of the absorbents
diminished except by sympathy, the fluid must remain the same. Thus
though there is suffering at the end of the glans from a stone in
the bladder, the glans is perfectly sound, and the mucous fluid that
escapes from it is of the same nature as in the ordinary state. On
the contrary, when dropsies depend upon a disease of texture of the
serous surfaces, as for example upon a tubercular inflammation, or even
an acute one, which has degenerated, &c. the effused serum is almost
always altered; it is milky, or there are albuminous flakes in it,
or a false membrane, &c. I have made this observation, which I think
interesting, upon nearly all the bodies I have opened.

In acute diseases, the serous surfaces receive also equally the
sympathetic influence of the affected organs. If we could then see
them, we should find that they were like the skin, more or less moist,
more or less dry, according to the different periods of the disease.
What proves it is, that at the death which follows the disease, the
serum of the pleura, the pericardium, the peritoneum, &c. varies
remarkably. Sometimes it is evidently increased, at others it is almost
nothing; this depends upon the time in which the subject died. If it is
whilst exhalation is very abundant, we find much serum; it is almost
nothing if life has been sufficiently prolonged to allow absorption to
take place. If the surrounding air did not dissolve the sweat, or if
the skin was in the form of a sac, we should find it with very variable
degrees of moisture, according as the subjects had died in sweat, or
with a suppression of the cutaneous exhalation.


ARTICLE FOURTH.

DEVELOPMENT OF THE SEROUS SYSTEM.


I. _State of this System in the First Age._

All the serous surfaces are extremely delicate in the fœtus. In opening
the thorax by a longitudinal section of the sternum and examining the
pleura in the mediastinum where it is free on both sides, it is found
to have less thickness than the transparent layers of the omentum or
the arachnoides in the adult. The peritoneum is a little thicker in
proportion, but yet its delicacy is very great. The comparison of soap
bubbles is hardly sufficient to convey an idea of the fineness of the
texture of the omentum and the arachnoides.

At this period the fluid that lubricates the serous surfaces is much
more unctuous and viscid than it is afterwards; by carrying the fingers
over these surfaces at the different ages, the difference is easily
perceived. It might almost be said that the tangible qualities of the
serous fluids then approximate those of the synovia. I know not to what
this difference belongs.

Besides, the quantity of these fluids does not appear to be so great in
proportion as that of the cellular fluids, with which they have however
so much analogy; which is probably owing to this, that the internal
motions being less numerous, on account of the inaction of most of the
organic muscles, less fluid is necessary to lubricate the surfaces.

The growth of the serous system is always in proportion to that of the
organs which it covers. The arachnoides is larger in proportion than
it will be in the adult; it seems even, like the brain, to become then
the seat of a more active labour; thus diseases are more frequent in
it. The increase of exhalation is more common in it than in all the
other serous sacs; hence hydrocephalus.

At birth, when the internal motions become suddenly very numerous,
on account of respiration, digestion and the excretions, I presume
that the serous surfaces become the seat of a more active exhalation.
Besides, as very little blood penetrates them, the sudden production
of the red blood and its entrance by the arterial system, where it
succeeds the black blood, produces less changes upon them than upon the
mucous surfaces and the muscular system.

The serous membranes grow like the other organs; for a long time
delicate and diaphanous, they gradually thicken as we advance in age,
and become of a dull white. Their suppleness diminishes as their
density increases; they resist the different reagents so much the less
as the subjects are younger. In infants, maceration and ebullition
reduce them much more quickly to a homogeneous pulp.

I have observed that in the fœtus which has become putrid, there is
often collected different gases in the serous cavities, as may be
proved by opening these cavities under water; a phenomenon much less
evident in the adult, in whom the cellular texture is often wholly
emphysematous by the putrefactive motion, without the escape of any
thing by the canula of a trochar which is plunged into the peritoneal
cavity or into that of the pleura, as I have many times ascertained. In
general, there is disengaged much more aeriform fluid from the organs
of the fœtus, than from those of the adult, in the experiments of
maceration.


II. _State of the Serous System in the after Ages._

In the adult, the serous system remains a long time without undergoing
any very sensible change; its membranes follow only the laws of
the organs they surround. Thus in the age nearest youth, the serous
surfaces of the chest are the most frequent seat of inflammations,
dropsies, &c. whilst in that bordering on old age the inferior
surfaces like the peritoneum, are the more often affected.

In old age, the serous system becomes dense and compact; its adhesions
to the neighbouring parts are more evident; thus it is less capable of
the different locomotions of which we have spoken. Its forces, which
are weakened, render absorption in it less easy; it is the frequent
seat of dropsy. When it is affected with some diseases, its want of
energy imparts to them a remarkable chronic character. There are many
old people at the Hôtel Dieu with tubercular inflammations of the
peritoneum, which they have had for a long time, whilst young persons
are overcome much quicker by the same inflammations. Thus cancers in
aged persons often remain almost inert, they frequently are not even
painful, whilst their periods are usually most rapid in adults.

The serous effusions are more rare than the infiltrations of the
sub-cutaneous cellular texture in old people; but they take place more
commonly than those of the intermuscular texture.

The serous system becomes ossified, but not like the arterial, the
cartilaginous, &c. from the natural effect of age. Its membranes are
not constantly found osseous in old age, and when this phenomenon takes
place, it happens at every age. It is a disease, a real tumour, whilst
in the arteries and the cartilages it appears to belong to a natural
series of functions. I have a preparation in which the arachnoides is
evidently osseous in many points, and as it is upon the dura-mater that
these productions are formed, their existence serves very well to prove
that the arachnoides is distinct from it; for at the place where they
are found, they can be easily separated from each other.


III. _Preternatural Development of the Serous System._

I shall not repeat here what I have said, in speaking of the cellular
texture, upon the formation of the different cysts. These cysts,
completely analogous to the natural serous membranes, should be really
considered as a preternatural development of these membranes in the
economy; they have the same appearance and almost the same texture,
furnish their fluid according to the same laws, and appear to be the
seat of a constant exhalation and absorption; since they are in vain
emptied by puncture, their fluids are always reproduced, until they are
removed. For example compare the cyst which has grown preternaturally
along the spermatic cord, with the tunica vaginalis filled with water
in hydrocele. If the size of these tumours, which are often found
together, is the same, it is impossible to discover any difference in
their form, appearance, texture, properties, functions, &c.




SYNOVIAL SYSTEM.


I place this system at the side of the serous, because it has the
greatest analogy with it, under the relations, 1st, of its form, which
is in each of these organs that of a sac without an opening; 2d, of
its texture, which appears to be essentially cellular; 3d, of its
functions, which consist in an alternation of exhalation and absorption.

What establishes a real line of demarcation between these two systems
is, 1st, that the fluids which lubricate their membranes appear to
differ in their composition, though there is much resemblance between
them. 2d. In dropsical diatheses which affect at the same time the
cellular texture and all the serous surfaces of the peritoneum, the
pleura, &c. the affection does not extend to the synovial membranes,
which indicates a difference of structure, though we do not know
what this difference is. 3d. And reciprocally in dropsies of the
articulations, an affection in general very rare, and in those of the
tendinous synovial capsules, there is no concomitant affection of
the membranes of the great cavities. 4th. The fluid of the articular
dropsies does not resemble that which fills the great cavities in the
same disease. 5th. The synovial membranes are much more rarely than
the serous, the seat of those slow and tubercular inflammations which
the serous surfaces so often exhibit. I have however seen two examples
of it in the synovial membrane of the knee. I believe that these two
systems are the only ones in which this disease is observed; so that
it is by its existence a character of resemblance, and by its rarity
or frequency, a distinguishing attribute. 6th. The different kinds of
adhesions of which I have spoken as taking place on the serous surface,
are not met with on the synovial surfaces, where we see only that which
identifies these two adhering surfaces, a mode which frequently takes
place in anchylosis, which is also as often occasioned by it, as by the
stiffness of the parts surrounding the articulation. 7th. The synovial
surfaces are not as often as the serous, the seat of those remarkable
locomotions of which we have spoken; which depends on this, that the
articular organs are not, like the most of those covered with serous
surfaces, subject to alternate dilatations and contractions.

The synovial system exhibits evidently two great divisions. To one
belongs the articular system, to the other that of the tendinous
grooves. Each shall be examined separately.


ARTICLE FIRST.

ARTICULAR SYNOVIAL SYSTEM.

I believe that I first described this essential portion of the synovial
system. I shall relate here what I have said of it elsewhere. I shall
examine first how it is separated from the blood, afterwards the fluid
itself, and then I shall describe the organ which furnishes it.


I. _How the Synovia is separated from the mass of Blood._

Every fluid differing from the blood, can be separated from it to be
afterwards transmitted to an organ, but in one of the three following
ways; 1st, by secretion, a function characterized by the existence of
a gland intermediate to the blood vessels that bring the materials to
it, and the excretories which carry off the result; 2d, by exhalation,
a function distinguished from the first, by the absence of this
intermediate gland, and by the immediate continuity of the blood
vessel and the exhaling duct; 3d, by transudation, a phenomenon purely
physical, almost always happening after death, rarely observed during
life, a simple transmission of a fluid by the pores of an organ,
towards which it is mechanically determined. Let us examine which of
these three modes is that chosen by nature to deposit the synovia upon
the articular surfaces.

_Is the synovia transmitted by secretion to the articular surfaces?_

We are indebted to Clopton Havers for the system which places in
the glands the sources of the synovia. Many authors had designated
obscurely before him these organs in the articulations; but he
made them the particular object of his researches, described them
in the different articulations, divided them into two classes, the
one principal, the other accessory, and assigned them characters
so evident, that according to him, they could not be forgotten.
Reddish bunches, spongy, formed by membranes folded upon themselves,
situated sometimes without, and sometimes within the articulations,
always arranged so as to be protected from too strong a compression,
and pouring out through ducts in the form of fringe the fluid they
secrete; such are the characters drawn by Havers, which all anatomists
since him admire, and the correctness of which the most modern and
distinguished authors have acknowledged in their works.

Some anatomists of this age have however thrown doubts upon these
glandular bodies. Lieutaud confounds them with the fatty cellular
texture. Desault did not distinguish them from it. Every thing confirms
me in the same opinion, which many considerations appear to establish
in an undoubted manner. The following are these considerations; 1st,
these reddish bunches are met with only in certain articulations. There
are many of them in which their existence cannot be established but by
supposition. 2d. The greatest number of the synovial membranes of the
tendons certainly do not exhibit any of them, though Havers, Albinus,
Juncke and Fourcroy admit them in all, founded no doubt upon analogy
and not upon inspection. Yet the synovia is separated equally in both
cases, and lubricates the surfaces of the articulations and of the
tendinous sheaths; this separation is then independent of glandular
action. 3d. If the best marked synovial glands are examined, such as
that of the cotyloid cavity, no trace can be discovered there of this
parenchyma of an unknown nature, but remarkable for its structure,
which composes in general the glands, and which distinguishes them
from every other part and forms their true organic character. 4th.
No excretory duct can be demonstrated in these organs. Those in the
form of fringes, admitted by Havers, are imaginary. Bertin himself
has acknowledged this truth, though he attributed to these bodies a
glandular structure. The transudation of the fluids injected by the
arteries in the neighbourhood of the articulation, proves the existence
of these ducts no better than it establishes them in the cavities of
the serous membranes in which it also takes place, and yet in which
it is well proved that no gland pours out the albuminous fluid
that constantly lubricates these cavities. 5th. Inflation resolves
completely these fatty bunches into cellular texture. Maceration
produces the same effect. When gradual and long continued ebullition
has removed all the fat from them, there remains only a mass of cells
pressed together, and similar to those of the common cellular texture.
6th. The glandular character is manifested in certain morbid cases, by
a peculiar swelling and hardening, of which the other organs except the
glands, such as the muscles, the tendons, &c. never offer an example.
The liver, the kidneys, the salivary organs, all the considerable
glands are remarkable for this. So true is this character, that it
serves to indicate glands, the delicacy of which conceals them in the
natural state. For example, the existence of the cryptæ of the stomach,
the urethra, and several other mucous membranes, is founded first upon
the analogy of the other membranes of this class, but principally upon
the preternatural development which these cryptæ acquire in certain
diseases. Never, on the contrary, do the pretended synovial glands
present to the observer a similar development. Always in the diseases
of the articulations, a common swelling seems to identify them with the
neighbouring cellular texture. They have not like the other glands,
affections distinct from those of this texture, no doubt because
they have not a peculiar vitality, because being mere elongations of
the neighbouring cellular texture, they partake of its nature and
properties, and ought consequently to partake of all its conditions,
as it in its turn ought immediately to receive the influence of their
affections.

The considerations which I have just offered successively form, I
think, sufficient data to resolve the problem proposed above, by
establishing as an incontestable proposition, that the synovia is not
transmitted by secretion to the articular surfaces.

Let us examine the second mode of transmission stated by authors.

_Is the synovia transmitted by transudation to the articular surfaces?_

It was an opinion anciently received, that the marrow of the long bones
oozes through the pores of their extremities and through those of the
cartilages which terminate them, to lubricate the articular surfaces.
Havers renewed this idea forgotten at the time he wrote, united this
source of the synovia to that which had placed it in the glands, and
thus formed of this fluid a mixture composed of two fluids differently
transmitted to the articulation. The most of those who succeeded him
partook of his opinion upon this point. Those even, such as Desault,
who rejected the existence of the articular glands and the secretion
of synovia, admitted the transudation of it founded upon the following
observations. 1st. A long bone, stripped of its soft parts and exposed
to the air, allows a fatty oozing to pass through the pores of its
cartilages which does not cease till the medullary juice is completely
exhausted. 2d. The mechanical compression of the cartilaginous
extremity of a long bone produces for a moment the same effect. Are
these facts, which are evident in the dead bone, also real in the
living one? Different considerations, which I will now state, induce
one to believe the contrary.

1st. The vital forces, the effect of which is to impart to all the
organs which they animate a degree of tone sufficient to resist the
entrance of the fluids, leave, when they are extinct, the fibres of
these same organs in a state of laxity that renders them everywhere
permeable. Thus transudation is now considered as hardly any thing
else than a phenomenon that takes place only after death, which, if
transformed into a vital one, would offer an evident exception to
the laws of nature that are especially characterized by simplicity
and uniformity. 2d. The fatty oozing takes place in the experiment
noticed above, not only through the pores of the cartilages, but also
through those of the whole surface of the bone; so that by reasoning
from what has been here observed upon the dead body, it is evident that
during life the whole bone would be, if you may so say, immersed in
an atmosphere of synovia, a consequence, which being proved false by
the most simple inspection, demonstrates the falsity of the principle
deduced from it. 3d. The articulations of the cartilages of the larynx
are lubricated like those of the bones, by the synovial fluid; and yet
here all transudation of marrow is impossible, as it does not exist
in the substances of the cartilages. 4th. The marrow is almost always
sound in diseases which, affecting the articulations alter the fluid
that lubricates them. And reciprocally the synovia does not take a
different character in the affections of the interior of the bones,
which have an influence especially upon the medullary organ. 5th.
Finally, the experiment that I have made, and which has been stated in
the article upon the marrow, evidently proves the non-transudation of
this fluid.

Desault, in order to explain the manner in which the synovia is
separated from the blood, added to this pretended transudation of
the marrow, an oozing furnished by all the parts contained in the
articulation, such as the capsular and inter-articular ligaments, the
internal fat, the cartilages, &c. A comparison will suffice to show the
value of this hypothesis. What should we say of a system in which to
explain the production of the serous fluid of the abdomen, the source
of it should be placed in the liver, the spleen, the intestines, and in
general in all the organs of this cavity? No doubt we should answer,
that a fluid of the same nature, could not be furnished by parts of
such different structure, that it is much more simple to search for
a single source in the single membrane that covers all the gastric
viscera. The application is exact and the analogy perfect between it
and the articular cavity.

We can, I believe, without fear of error, conclude from all that has
been said above, that the synovia is not transmitted by transudation to
the articular surfaces.

I will now examine the last mode pointed out for the separation of the
synovia.

_Is the synovia transmitted by exhalation to the articular surfaces?_

The solution of the two preceding problems seem naturally to lead
to that of the question which we here propose. The certainty of
the two following data may, I think, be relied on; 1st. Secretion,
exhalation and transudation are the only means by which a fluid
different from the blood can be transmitted to an organ. 2d. Secretion
and transudation are foreign to the transmission of the synovia.
Now from these two certain data, can we not draw this conclusion as
certain, that exhalation is the mode by which the synovia is carried
to the articulations? But let us add to these negative proofs some
considerations which establish this proposition positively.

The most striking relations are observed between the synovia and the
fluid that lubricates the parietes of the serous membranes. 1st. The
relation of composition. These two fluids are essentially albuminous.
Albumen predominates in both, though a little different in each, as
Marguerron has demonstrated. Havers had previously pointed out this
analogy; he knew that these two fluids are coagulable by alkohol,
the acids, and caloric, without knowing the principle to which this
property is owing. 2d. The relation of functions. Both are destined to
lubricate surfaces on which much motion takes place, to diminish the
friction which is the inevitable consequence of it and to prevent fatal
adhesions. Both are in the same state on their respective surfaces;
it is merely a dew spread upon these surfaces, and soon taken up from
them. 3d. The relation of affections. Inflammation dries up the source
of both, and produces adhesions, more common in the serous membranes
and more rare in the articulations in which they produce anchylosis.
Both are subject to preternatural enlargement, which is designated
by a common word, viz. dropsy. 4th. The relation of absorption. The
lymphatic system is for both the way by which they re-enter the
circulation, after having remained sufficiently long upon their
respective surfaces.

Do not these various resemblances, which with some slight differences
of composition only, so evidently connect the synovia with the fluid
of the serous membranes, lead us to this very simple consequence, viz.
that these two fluids being analogous in all other respects must be
so also as to the manner in which they are separated from the mass of
blood? Now it is a point in physiology at the present day generally
acknowledged, that the fluid of the serous membranes is brought to them
by exhalation; then we are evidently lead by induction to this which
answers the question proposed above; The synovia is transmitted by
exhalation to the articular surfaces.

This rigorous and accurate conclusion drawn from obvious and uniform
facts will become, I think, a demonstrated truth, when to the analogies
already established we shall add that of the membranous organ, the
essential seat of the exhalation of the synovia.


II. _Remarks upon the Synovia._

Thus separated from the mass of blood, the synovia has the appearance
of a white, viscid and transparent fluid. It ropes, like some syrups,
when it flows from the articulations. This unctuous property renders it
peculiarly fit to lubricate the articular surfaces which rub together,
and to protect them from violent shocks.

Its quantity varies; there are articulations which contain much of it;
that of the ankle has always appeared to me to have the most of it.
Then come the ilio-femoral, the scapulo-humeral, the humero-cubital,
&c. There are others in which there is scarcely any; such are the
sterno-clavicular, the sterno-costals, the costo-vertebrals, &c. It
is not the smallness of the synovial surfaces that occasions in these
articulations the constant dryness that is observed in them; for the
synovial sacs of the larynx, which are much smaller, are much more
moist.

Besides, the synovia does not vary in quantity in each articulation,
like the serum in the serous membranes. Those who have opened
peritoneums, pleuras, pericardiums, &c. must have seen that hardly
two are similar; sometimes there is only a mere dew, at others there
is a real collection of fluid. Here on the contrary there is always
nearly the same quantity; which is owing to this, that the synovial
surface does not feel as easily as the serous surfaces, the sympathetic
influences of the other organs when diseased.

The synovia is not subject to the different alterations which the
serous fluids exhibit. I have never seen upon the articular surfaces
what are called false membranes from inflammation. The preternatural
collections of synovia never contain those white flakes, so common in
the serous collections. I do not know of an example of milky serum
effused in an articulation. One of the most frequent alterations of
the synovia is that, I think, in which it takes the consistence of a
jelly and is of a reddish colour, analogous, if I may be allowed the
comparison, to currant jelly. Now this alteration is wholly foreign to
the serous fluids.

These essential differences which the synovia and the serum exhibit
in their alterations, evidently suppose a diversity of nature in the
principles which compose them in the natural state. The viscidity of
one and the greater fluidity of the other, also declare it, as Fourcroy
has observed. This diversity of nature appears to depend especially
upon a peculiar substance which enters into the composition of the
synovia, which few animal fluids possess, which Marguerron who has
observed it designates by the name of albumen of a peculiar nature, and
which should be the object of new researches.

I shall not give here the details of the analysis of the synovia; they
belong to animal chemistry.


III. _Of the Synovial Membranes._

We have seen all the great cavities lined by the serous membranes,
which form by their folds species of sacs without an opening, and which
embrace both the organs and the parietes of these cavities. There
exists in all the moveable articulations membranes precisely analogous,
the uses of which are the same, the nature of which is not different
and which I call synovial, because their parietes constantly exhale and
absorb synovia.


_Forms._

Every synovial membrane then, should be considered as a sac without an
opening, spread upon the organs of articulation, upon the diarthrodial
cartilages, upon the internal face of the lateral and capsular
ligaments, upon the whole of the inter-articular ligaments when they
exist, upon the prominent fatty bunches in some articular cavities, &c.
It is from it that these different organs borrow the smooth, polished
and shining appearance which characterizes them in these cavities, and
which they have not elsewhere. Just as by dissecting carefully the
gastric organs, the peritoneum can be removed, its sac remaining whole,
so we can conceive of the possibility of separating this membrane,
notwithstanding the intimate adhesions it forms in some places. All
the parts that it embraces are out of the articular cavity, though
projecting into this cavity, as the lungs are found on the exterior
of the sac formed by the pleura, the liver on the exterior of the
peritoneal sac, &c. &c.

The synovial membrane is found in all the moveable articulations, the
greatest number of which has only it and the lateral ligaments. What is
commonly called the fibrous capsule is only met with around some of the
articular surfaces. The connexions of the humerus, the femur, and one
or two other bones, the extremities of which are joined by enarthrosis,
present the only examples of it. There are seen in these articulations
two very distinct coverings. One which is fibrous is external, and is
found arranged in the form of a sac open above and below, embracing
by its two great openings the surfaces of the two bones, and being
intermixed around them with the periosteum, the fibres of both
interlace with each other. The other cellular, which is the synovial
membrane, lines the first on the interior, separates afterwards from
it when it arrives towards the two diarthrodial cartilages, and is
reflected upon them, instead of being united to the periosteum. Boyer
has pointed out this arrangement in regard to the femur.

In all the ginglymoid articulations, as in those of the elbow, the
knee, the phalanges, the hand, the foot, &c. &c. the fibrous capsule
is wholly wanting. The fibres, instead of extending and interlacing
in the form of a membrane, are collected into fasciculi more or less
thick, which form the lateral ligaments. There is only found in them
the internal layer of the enarthrodial articulations, that is to say
the synovial membrane, which does not contract here any adhesion with
the periosteum, but is reflected upon the cartilages. By taking it at
the place of this reflection, it can be detached far enough to prove
that it has an external organization wholly different from that which
the idea of a capsular ligament at first presents to the mind. This
arrangement is very easily perceived by the least dissection, at the
knee behind the tendon of the cruræus and the inferior ligament of the
patella, at the elbow under the tendon of the triceps, at the phalanges
under that of the extensor, &c. All the arthrodial articulations have
also an analogous organization, as will be seen in the Descriptive
Anatomy; so that it is ascertained that the fibrous capsules exist but
in a very small number of articulations, that almost all have only
synovial sacs which are spread out and reflected upon the osseous
surfaces, without being attached around them, as all authors have said.

I have proved this remarkable difference of the articulations by many
dissections. Some anatomists were in the way to discover it, when they
observed that the different capsules appeared to be wholly formed of
cellular texture. It is in fact the texture of the synovial membrane,
which differs essentially in this from the fibrous capsules. The mode
of capsule for all articulations may be preserved, if it is wished, but
different ideas must then necessarily be attributed to it. Compare, for
example, the fibrous capsule of the femur with the synovial capsule
of the knee; you will find on the one hand, 1st, a cylindrical sac
with two great openings for the osseous extremities, and with many
small ones for the vessels; 2d, a fibrous interlacing, similar to
that of the tendons, the aponeuroses, &c. 3d, a mode of sensibility
analogous to that of these organs; 4th, the use of retaining strongly
in place the articulated bones, which have only this bond to strengthen
their union. On the other hand you will observe, 1st, a sac without
an opening; 2d, a cellular structure, the same as that of the serous
membranes; 3d, a sensibility of the same nature as theirs; 4th, the
simple function of containing the synovia and separating it, the bones
being tied by strong ligaments. Besides, the different reagents have
upon the fibrous capsules an influence wholly different from that which
they exert upon the synovial. Ebullition yellows them, renders them
semi-transparent, softens them like tendons and gradually melts them
like gelatine. The synovial ones boiled remain whitish, and furnish but
little of this substance. I would observe that the yellowish tinge and
semi-transparency of the boiled fibrous capsules are a certain means of
distinguishing the articulations in which they exist and those which
are destitute of them.

The existence of the synovial capsule in the greatest number of
articulations in which it is found alone, is placed beyond a doubt by
the slightest inspection. In those in which it is united to a fibrous
capsule, it is very clearly distinguished in several places. Thus in
the thigh, it is found upon the interarticular ligament, upon the
fatty bunch in the cotyloid cavity, and upon the neck of the bone
at the places where it leaves the fibrous capsule, to be reflected
upon the cartilages, &c. but its adhesion to these cartilages and to
the internal face of the capsule, may excite some doubts as to its
arrangement in the form of a sac everywhere closed, which we have
attributed to it; it is then essential to offer some considerations
that may dissipate these doubts.

1st. However strong the adhesions of the synovial membrane may be,
they can be destroyed without a solution of continuity, by a slow,
careful dissection begun at the place where the membrane is reflected
from the cartilage upon the capsule. It can be taken away in parts
after long continued maceration. 2d. In consequence of certain
inflammations, this membrane acquires a thickness and opacity which
enable us to distinguish it from all the neighbouring organs, from
those even to which it adheres the most. 3d. The synovial bags are
all as adherent as the articular synovial one, to the cartilages of
their sheath and to this sheath itself; yet every one acknowledges
their distinct existence. 4th. There are articulations with a fibrous
capsule, in which the fibres are separated so as to leave a space
between them through which the synovia would escape, if the synovial
membrane did not line them. When air is forced into the articulation,
this membrane rises up in these spaces and exhibits a texture wholly
different from that of the capsule. Bertin observed this, but thought
that these pellicles were insulated, and did not see that they depended
upon the continuity of the membrane which is extended over the whole
articulation. 5th. We have observed in the article upon the serous
system, that the smooth and polished appearance which the surface
of the organs and the cavities exhibit, is always given to them by
these membranes, and that they never derive it from their peculiar
structure; now we shall see that the synovial membrane has almost
the same texture as the serous; then it appears that in the places
in which the articular organs exhibit this character, it is from it
that they receive it, though it cannot be distinguished as well upon
these organs, as where it is free. Besides, the articulations that are
evidently destitute of this membrane, have not this smooth and polished
appearance. Such are the surfaces of the symphysis pubis, and of the
sacro-iliac symphysis which are found, though contiguous, unequal,
rough, &c. We have also proved that this organic form is never owing to
compression.

From these different considerations we may be easily convinced, I
think, that notwithstanding the adhesion of the synovial membrane
at different points, it should be considered in a manner precisely
analogous to that of the serous membranes, that is to say as a real
sac without an opening, everywhere contiguous and spread upon all the
organs of the articulation. Besides, do not the fibroserous membranes
exhibit similar adhesions, though the separate existence of the two
layers which compose them is generally admitted?

From the idea we have formed of the synovial membrane, it is easy to
conceive how certain organs pass through the articulation, without
the escape of the synovia by the opening which receives or by that
which transmits them. The synovial membrane then reflected around
these organs, forms for them a sheath which separates them from the
fluid and keeps them distinct from the articulation. Thus the tendon
of the biceps is no more contained in the articulation of the arm with
the scapula, than the umbilical vein, the urachus, &c. are in the
peritoneal cavity. With the least care it may be separated from the
portion of membrane which forms its sheath.

The preceding considerations lead us also to find a perfect identity in
the synovial capsules of the tendons and the articular synovial ones.
In the preceding example, these two kinds of membranes are evidently
continuous; for the capsule of the groove of the biceps is of the same
nature as that of the tendons which have a separate one from it, as the
flexors, for example.


_Organization._

We have just seen, that the synovial membrane resembles very much in
its external conformation the class of serous membranes, it does not
less so in its internal organization. This organization is cellular,
as is proved by dissection, inflation and especially maceration. The
sac which the ganglions form is evidently only a production of the
cellular organ; now it is known that this sac exhales and contains a
fluid similar to the synovia. Wherever the synovial membrane is free,
it is attached externally to this organ and is confounded with it in so
direct a manner, that by raising successively its different layers they
are seen to be gradually condensed and finally united together to form
it. So that in the serous membranes no fibre is visible. It becomes
transparent when it is separated accurately on both sides, which is
easily done at the knee to a great extent.

I shall not go back to the various proofs which establish the
cellular structure of the serous system; almost all these proofs are
applicable to the synovial system, which appears to be but a net-work
of absorbents and exhalants. Hence it is easy to understand what the
red and fatty bunches are that are found around the articulations.
They perform in regard to this membrane the functions of the abundant
cellular texture which envelops the peritoneum, the pleura, &c. &c. It
is there that the blood vessels divide ad infinitum before arriving
at the membrane where their ramifications, successively decreasing,
finally terminate in the exhalants.

If a remarkable redness sometimes distinguishes these bunches from
the cellular texture, it is because the vessels are more concentrated
and nearer together in them. For example, in the articulation of the
hip, the synovial membrane of which, almost everywhere adherent, only
corresponds in the fissure of the cotyloid cavity with the cellular
texture, nature has placed there almost all the arterial ramifications
that furnish the synovia; hence the reddish tinge of the cellular bunch
that is found there. On the contrary, at the knee where much cellular
texture surrounds the whole external face of the synovial sac, the
vessels more scattered leave to this texture the same colour as that
of the external face of the serous membranes, &c. This redness of
some pretended synovial glands, the only character that distinguishes
them, is then as it were merely accidental; it no more indicates their
glandular nature, than it proves it in the pia-mater, in which it is
owing to the same cause.

Though the synovial membrane is very analogous to the serous surfaces,
it must however exhibit differences of texture, since the fluid
it exhales is a little different. In fact, by examining it at the
femoro-tibial articulation, where it can be found in considerable
pieces, it is seen to be more dense and compact than the serous
membranes. Its texture has not the suppleness of theirs; when dried, it
is much more brittle; it remains stiff, whilst the serous texture is
moved in all directions without the least effort. It resists maceration
longer.


_Properties._

The properties of texture become evident in articular dropsies, in
which the synovial membranes are at first much distended, and in
which they contract after the puncture, an operation however that is
very rare. Yet it appears that these membranes are only susceptible
of a slow and gradual extension. We know that suddenly separated in
luxations, their parietes tear instead of stretching; they unite again
after the reduction.

Among the vital properties, the organic sensibility is the only
one of this system in the ordinary state, as I have proved by many
experiments on living animals in which these surfaces have been laid
bare and irritated by various agents. But the increase of life which
inflammation produces by raising this sensibility, transforms it into
animal sensibility; this is what is observed, 1st, in the wounds in
which these membranes are exposed to the contact of the air; 2d, in
the long continued irritation they experience from foreign bodies
preternaturally developed in the articulation; 3d, in the various
affections of the articular surfaces, &c.

This kind of sensibility of the synovial membranes serves to confirm
what I have already established above, viz. that most of the
articulations, the ginglymoid especially, are destitute of fibrous
capsules. In fact, I have observed that these capsules, as well as
the lateral ligaments, have a kind of animal sensibility, which is
developed by pulling them; so that if all the neighbouring organs of an
articulation, except the synovial membrane and the lateral ligaments,
are removed and this articulation afterwards twisted, the animal
gives signs of the most acute pain. But afterwards cut the ligaments,
and leave only the synovial membrane, the twisting no longer gives
pain; then there is no fibrous capsule united to the synovial. This
experiment, which is easily repeated upon the fore or hind legs,
enables us to recognise everywhere the articulations in which the
synovial membrane exists alone, and those in which it is found united
to a fibrous capsule. This being of the same texture as the lateral
ligaments, produces the same pains when it is pulled, as is proved
elsewhere by experiments made upon the articulations clothed with these
capsules.

The alternate exhalation and absorption which takes place upon the
serous surfaces, prove the insensible contractility in them.

I have already observed that the synovial surfaces perform but a small
part in the sympathies, that they feel but very slightly the affections
of the other organs. Whilst in the acute affections of the important
viscera, the skin, the mucous surfaces, the cellular texture, the
nerves, &c. &c. have a greater or less sympathetic derangement, all
the synovial membranes remain unaffected; they do not become the seat
of irregular pains, nor of a more active or slower exhalation. They
resemble in this respect the osseous, cartilaginous, and even fibrous
systems. Thus it is not necessary that the physician should seek in the
synovial system a frequent seat of the accessory symptoms in diseases,
of that class of symptoms which does not belong to the injury of the
diseased organ itself, but to its relations with other parts.

In the pains of the articulations, there are certainly cases in which
the synovial membrane is diseased, and others in which the fibrous
organs alone are affected. The distinction of these cases should be
sought.


_Functions._

The synovial membrane adds nothing to the solidity of the articulation.
The fibrous capsules and the lateral ligaments alone serve this
purpose. The smooth surface which the articular extremities derive
from this membrane, favours their motions; it can even in this way
assist the muscular action; thus the portions of synovial membrane
which are found at the knee behind the cruræus, at the elbow under the
triceps, at the phalanges under the flexors, &c. perform in respect to
these muscles, the same functions as the tendinous synovial bags. They
are to their tendons, what the cellular sac which separates the tendons
of the psoas and the iliacus from the crural arch, is to them.

The principal use of the membrane of which we are treating is in
relation to the synovia. It exhales by numerous orifices this
fluid which remains there for some time, and afterwards re-enters
the circulation by absorption. Its parietes are then the seat of
exhalation, as the kidneys, for example, are that of the secretion of
urine. The reservoir of the exhaled fluid is the sac without opening
which it forms, as the bladder is that of the urine that comes from the
kidneys. The excretory vessels of this same fluid are the absorbents
which carry it into the mass of blood, as the urethra carries the urine
from the bladder. There is under these different relations more analogy
than there at first seems to be, between secretion and exhalation.

The phenomena of the continuance of the synovia in this membranous
reservoir, have relation to the synovia itself or to the articular
surfaces. The first consist in a peculiar but unknown alteration which
it undergoes between the exhalant and absorbent systems. The second
contribute to facilitate the articular motions. The unctuous and
slippery coat which the serous surfaces receive from the synovia, is
remarkably adapted to this use, as I have observed.


_Natural Development._

In the fœtus and in infancy most of the synovial membranes are much
larger in proportion than in the after ages, because the articular
surfaces have a greater extent in the cartilaginous than in the osseous
state; but they are then extremely delicate. The synovia is not,
as the serous fluids are at this age, more unctuous and of greater
consistence; it appears even to be less so. Before birth it is in small
quantity, no doubt because the motions are trifling.

In old age I have observed that the synovial membrane becomes more
dense and compact. It loses in part its white colour and becomes grey;
less synovia is exhaled from it. It is not like the serous surfaces,
exposed to dropsies. The rigidity it acquires makes motion painful.
It never ossifies except preternaturally. The phosphate of lime which
gradually invades cartilage, does not take hold of it. I do not know
an instance of an old person in whom bone has been found naked in an
articulation.


_Preternatural Development._

I have already observed in the article on the fibrous capsules, that
when the head of a bone remains displaced in a luxation, it is not a
membrane analogous to these capsules that is developed around it; it
is a real cyst, smooth on its internal surface, moistened with serum,
formed at the expense of the cellular texture, and presenting, with a
little more thickness, the true appearance of the synovial membranes;
it is a preternatural synovial membrane. The motions imparted to the
displaced limb appear to increase the serous exhalation in this new
membrane; hence no doubt the great advantage of these motions, in
order to re-establish in part the mobility of the bones which remain
out of their sockets. I have seen a dancer, the head of whose humerus
was lodged in the hollow of the axilla, after a luxation that was not
reduced, perform very varied motions with it.


ARTICLE SECOND.

SYNOVIAL SYSTEM OF THE TENDONS.

This system noticed by many authors and described by Fourcroy,
Soemmering, &c. is precisely of the same nature as the preceding, from
which it differs only by its situation; it is often even confounded
with it. Thus the synovial membrane of the tendon of the biceps is
continuous with that of the scapulo-humeral articulation; thus those
of the gemelli are so with the synovial membrane of the femoro-tibial
articulation; it is the same membrane which belongs at the same time to
the tendon and to the articulation. A remarkable example of it is seen
in the extensors of the leg and the ham, to the tendons of which the
same articular synovial membrane of the knee serves for a capsule.

But very few tendinous synovial membranes are found in the trunk;
almost all are on the extremities where they serve to assist the
slipping of the tendons. They are met with, 1st, where a tendon is
reflected at an angle upon a bone, as around those of the great lateral
peroneus, the peroneus medius, the obturator internus, the great
oblique of the eye, &c. 2d, where a tendon slips upon an osseous
surface without being reflected, as at the extremity of the tendo
Achillis, as under that of the great glutæus, and those of the psoas
and iliacus united; 3d, where a tendon slips in a fibrous capsule,
as in those of all the flexors, &c. Their extent is uniformly in
proportion to that of the tendons upon which they are spread.


_Forms; Relations; Synovial Fluid._

The tendinous synovial membranes, are, like the articular ones, sacs
without an opening, spread on the one hand on the tendon and on
the other upon the neighbouring organs. These sacs are differently
shaped according to the arrangement of the tendon, but their general
conformation is uniform. We see from this that every tendinous synovial
membrane has two faces, one which forms the interior of the sac, which
is everywhere free and contiguous to itself, the other which lines the
adjacent organs.

The free surface is constantly moistened by a fluid precisely similar
to that of the articulations, furnished like it by exhalation, and
not as authors have said by red bodies situated in the neighbourhood,
bodies of which oftentimes there is no trace visible, and which, when
they exist, have nothing glandular in them. This fluid is in general
much less abundant than in the articulations, at least in the dead
body. But there are varieties in the different synovial bags; those of
the tendo Achillis, of the tendons of the psoas and iliacus united, of
that of the obturator internus, &c. are always more moist than those of
the flexor tendons, &c.

Is it to the absence of synovia that must be attributed the species
of crepitation which the tendons sometimes make in their motions? I
know not. I would only observe that this crepitation has some analogy
with the crackling noise of the joints of the fingers when they are
bent quickly, a noise, which does not depend, as might be supposed,
on the friction of the osseous surfaces; in fact, when it has been
once produced, it cannot be again, though there may be friction again.
Besides it is known that this crackling noise arises from the forced
elongation of the phalanges, and consequently from the separation of
their articular surfaces, as well as from the flexion.

The increase of the fluid of the tendinous synovial membranes forms
a species of dropsy which is called ganglion, a tumour which never
exists in the synovial membranes of the fingers, no doubt on account
of the want of extensibility of the fibrous capsules. It should not
be thought however that all these tumours, which are cured by bursting
them by strong pressure and thus effusing the fluid into the cellular
membrane, have for their base a natural synovial membrane. Most
frequently they are preternatural; they are cysts which are formed in
the cellular texture. In fact these tumours are often found in the
course of the great extensor of the thumb, where there is no synovial
membrane. After rheumatic pains I have seen a considerable collection
of fluid in the small synovial membrane of the tendo Achillis; it
gradually disappeared. I have observed another analogous one in the
bag of the psoas of a dead body. The fluid was reddish and of the
consistence of currant jelly. The action of nitric acid immediately
coagulated it into a white mass, analogous to the white of an egg
hardened.

The adhering surface of the tendinous synovial membranes is spread,
1st, on the one hand upon the tendons, with which it is more or less
intimately united. It is easily detached from those of the internal
obturator, the psoas, &c. It is closely connected with those of the
flexors. 2d. On the other hand, it commonly lines the periosteum,
which, in this place, is penetrated with gelatine, and forms a
fibro-cartilage. Its mode of relation is there analogous to that of the
articular synovial membrane with the cartilage of the bone. Sometimes
it is reflected upon a fibrous capsule after having lined the tendon;
such are those which are in the neighbourhood of the scapulo-humeral
articulation. In some cases, after having lined the tendon, they
mount up to the fleshy fibres, as on the obturator internus. 3d. By
reflecting from the tendon upon the neighbouring organs, they answer
in general instead of much cellular texture; but in the grooves of the
flexors, it is the fibrous sheaths which they clothe.

In all the great motions, the tendinous synovial membranes, stretched
more or less, undergo various locomotions, always less however than
those of the serous surfaces.

The very various forms, which the sac without opening of the
tendinous synovial membranes exhibits, can be reduced to two general
modifications. 1st. Some are rounded sacs, species of bladders; such
are those upon the supra-spinatus, the psoas, iliacus, obturator
internus, &c. All these membranes are remarkable for this, that they
never cover the tendon entirely, but only on one side; that they never
form internal folds and that they are never surrounded by fibrous
sheaths. 2d. The others, belonging especially to the flexors, and to
the different tendons which traverse the sole of the foot, form at
first a kind of cylindrical sac which lines the canal half fibrous,
half cartilaginous in which the tendon slips; then they are reflected
around it, cover it wholly and form for it a true sheath which prevents
it from being moistened by the synovia. This kind of tendinous synovial
membrane represents then truly two canals, at the superior and inferior
extremities of which are found two cul-de-sacs which unite them and
complete the sac without an opening. Internal folds are here frequently
found going from one canal to the other. All the synovial membranes of
the flexors have one of them under the tendon.


_Organization; Properties; Development._

The organization of the tendinous synovial membranes is precisely
analogous to that of the articular ones. Principally cellular, the
texture of these membranes is without any apparent fibre; its softness
is very evident; very few blood vessels are distributed to it, though
the contrary has been said; absorbents and exhalants especially
predominate in it. These, filled with blood in inflammation, give to
the membrane, a reddish tinge, more or less deep. In this state the
synovia is not exhaled; sometimes even adhesions are formed, as I have
observed in a subject in whom the fibrous sheaths and their tendons of
the index and the middle finger seemed to be united. The inflammatory
phenomena of the tendinous synovial membranes are especially remarkable
in whitlows, a disease, one species of which has evidently its seat in
the synovial membrane of the fingers, is analogous to the inflammation
of the pleura, the peritoneum, and to that of the articulations. It is
more dangerous than the inflammation of the synovial membranes in the
form of bladders or bags, because the fibrous sheath which surrounds
the inflamed membrane, not being able to stretch and yield to the
swelling, like the cellular texture which surrounds the synovial bags,
produces real strangulations, which it is often necessary to remove. I
do not know whether the synovial texture of the tendons is exposed to
the slow and tubercular inflammations, common to the articular serous
and synovial systems. Its vital properties and those of texture appear
to be precisely the same as those of this last. Like it, it receives
with difficulty the sympathetic influence of the other organs; it
is unaffected during the derangement of the other systems in acute
diseases; it remains sound in their alterations arising from chronic
affections. I would observe also that all its affections are almost
local. For example, there is not, as in the serous system, species of
dropsical diathesis, that is to say of cases in which all the synovial
sacs are filled at the same time.

The tendinous synovial membranes, fine and delicate in the fœtus and in
infancy, readily yield to the numerous motions which constantly succeed
that age. More dense and compact in the adult, they become rigid in old
age, exhale less fluid, are dry, and do not contribute a little, by the
state in which they are, to the general slowness of the motions which
that age brings with it.

There are many synovial membranes the existence of which is variable;
such as, for example, that of the great glutæus, in the place of which
there is often found only a cellular mass. These membranes are in
general very dry when they exist. Synovia can scarcely be discovered in
them. They resemble in this respect the articular synovial membranes of
the vertebræ, the clavicle, &c.




GLANDULAR SYSTEM.


This system, one of the most important in the animal economy, differs
from most others in this, that the texture which is peculiar to it is
not precisely the same in all the organs that compose it. The fibres
of a muscle of animal life would as well serve for the structure
of any other muscle of the same system. The tendinous fibres, the
cartilaginous, osseous textures, &c. are everywhere the same. On the
contrary, the texture of the liver would not serve to compose the
kidney, nor that of this last the salivary glands. The glandular system
then has a resemblance in its different parts only by certain general
attributes which have many exceptions.

Authors have given the name of glands to organs to which it does not
belong; such as the thyroid, the pineal, the lymphatic glands, those
especially that are in the neighbourhood of the bronchia, the thymus,
the suprarenal, &c. We should call by this name only a body from which
flows, by one or many ducts, a fluid which this body separates from
the blood which it receives by the vessels that go to it. 1st. On the
head, the salivary, the lachrymal, the Meibomian and the ceruminous
glands of the ear, and the amygdalæ.; 2d, the mammæ on the thorax; 3d,
in the abdomen, the liver, the pancreas and the kidneys; 4th, in the
pelvis, the prostate and the testicles; 5th, on the whole trunk and the
face, the very numerous collection of mucous glands; these are nearly
all that are dependant upon the glandular system; all the other organs
which belong to it by this name, are foreign to it in their texture,
their properties, their life and their functions. In this point of
view, the division of Vicq d’Azyr is inaccurate.

The extremities contain nothing which belong to this system, no
doubt because the fluids which it separates almost all serve for the
functions of organic life, whilst in the extremities every thing is in
relation to animal functions.


ARTICLE FIRST.

SITUATION, FORMS, DIVISION, &C. OF THE GLANDULAR SYSTEM.

The glands have two different positions. Some of them are
sub-cutaneous, as the mammæ, the salivary glands, &c. the others
deep seated, as the liver, the kidneys, the pancreas and almost all
the mucous ones are removed from the action of external bodies. The
greatest number occupy places where there is constantly much motion,
as the salivary glands on account of the jaw, the mucous on account of
the neighbouring fleshy layer, the liver on account of the diaphragm,
&c. It is this which has made it believed that this motion, foreign
to their functions, was destined to produce the excretion of their
fluids. But, 1st, the glands of the palatine arch, the pancreas,
the testicles, the kidneys even, can hardly borrow accessory aid on
account of their position. 2d. We know that the sight alone of grateful
food makes the saliva flow. 3d. Sialagogues produce the same effect.
4th. When the bladder is paralytic, the mucous juices pour into it as
before, oftentimes more copiously. 5th. The semen flows involuntarily.
6th. The excretion of the mucous juices is as easy in the pituitary
membrane as any where else, though the fleshy layer, almost everywhere
spread under the mucous system, is wholly wanting here. A thousand
other analogous facts prove this truth placed beyond a doubt by Bordeu,
viz. that the vital action is the essential cause of every excretion.

Accessory aid should not however be entirely rejected. In fact, in
salivary fistulas, there is evidently more fluid thrown out during
mastication than at any other time. It is evident that in the excretion
of urine, the abdominal muscles perform the principal part. When the
gall-bladder is emptied, I believe that the neighbouring motions are
much assistance to it. In general, whenever the fluids are found in
considerable quantities, if the parietes of the organs which contain
them are not very strong, like those of the heart, the motions of the
neighbouring organs are necessary to overcome the resistance which they
offer. On the contrary, in the capillary vessels in which the fluids
are in small quantities, the organ that contains them is sufficient, by
its reaction, for the motion.

There are single glands like the liver, the pancreas, &c. and others
in pairs, as the kidneys, the salivary, lachrymal glands, &c. These
resemble each other in general on both sides; but their resemblance
is not to be compared for precision to that of the organs in pairs
of animal life. One of the kidneys is lower than the other; their
arteries, veins and nerves are not analogous either in length or size;
frequently fissures exist in one that are wanting in the other, &c.
The same observation is true with respect to the salivary glands.

The glandular forms are not fixed and invariable; they exhibit
a thousand different modifications in their size, direction and
proportions; they have never the precise and exact conformation of the
organs of animal life. This fact can be disputed by no one who has
examined a number of dead bodies. The following are the means by which
I have made this most evident to myself. We know that the organs vary
much in size, in different individuals; now, in these varieties the
proportions are always accurately kept in animal life, whilst it is
rare that they are so in organic life. Let us take an organ for example
in each of the two lives. I have always seen that in a small brain the
corpus callosum, the thalami nervorum opticorum, the corpora striata,
&c. are in proportion to the whole size of the organ. On the contrary,
nothing is more common than to see a large lobe of Spigelius with a
small liver, and vice versa a large liver with a small lobe. There is
no anatomist who has not had frequent occasion to make this remarkable
observation. A kidney is larger sometimes in its superior part,
sometimes in its inferior, &c. It is in the whole of the organ that
these varieties of size take place in animal life; it is oftentimes in
insulated parts only in organic life. The reason of this appears to me
to be that the harmony of action is necessary, as I have demonstrated,
for the animal functions; so that if one side of the brain is more
developed than the other, if one eye, one ear, one pituitary membrane,
&c. are more developed than their corresponding organs, the perception,
the sight, the hearing, the smell, &c. would be inevitably deranged;
whilst the secretion of bile, of urine, &c. takes place equally well,
though one part of these glands may be larger or smaller than the other
parts.

There is a remark to be made respecting the glands with regard to these
varieties of form, it is, that those which are covered by a membrane,
as the liver, the kidneys, even the pancreas, are less exposed to
them than those which are buried in cellular texture without having
around them a membranous covering, as the salivary, the lachrymal, the
mucous glands, &c. I have often examined these last in the mouth and in
the course of the trachea; I never found them alike in two subjects.
We know that the parotid sometimes extends upon the masseter, and
sometimes does not, that it descends more or less into the neck, that
it is of a greater or less size there, &c.

When one gland of a pair is wanting or becomes diseased, sometimes the
other increases considerably in size, as I have seen in the kidneys.
This takes place also in the treatment by compression of salivary
fistulas, a treatment which does not however always succeed. In other
cases, the sound gland increases its action and secretes more fluid,
without increasing in size.

The exterior of the glands not covered by membranes is unequal and
lobulated; it conforms to the muscles, the vessels, the nerves, and
even the bones, as the parotid which is placed under the angle of the
jaw. Less cellular texture is in general found around them, than around
organs with great motion. That which is in contact with them is more
dense and compact than that of the organic interstices. It closely
resembles the sub-mucous texture, that exterior to the arteries, the
veins, the excretories, &c. but it is not however so resisting. It
receives fat with difficulty, and forms a kind of membrane, which,
insulating to a certain extent the vitality of the gland, performs in
great measure in this respect the functions of the peritoneum around
the liver, of the peculiar membrane of the kidneys, the spleen, &c.


ARTICLE SECOND.

ORGANIZATION OF THE GLANDULAR SYSTEM.


I. _Texture peculiar to the Organization of this System._

The glandular texture is distinct from most of the others in this, that
the fibrous arrangement is wholly foreign to it. The elements that
compose it are not placed at the side of each other, in longitudinal or
oblique lines, as in the muscles, the fibrous bodies, the bones, the
nerves, &c. They are found agglomerated, united by cellular texture,
and adhere but very slightly. Thus whilst the organs with distinct
fibres resist much, especially in the direction of their fibres,
these are torn with the least effort, and break even with ease. Their
rupture is unequal, full of prominences and depressions, a difference
which distinguishes them from cartilage, the rupture of which is in
general smooth. This rupture is not equally easy in all the glands.
The prostate, the amygdalæ, the mucous glands resist much more than
the liver or the kidneys, which principally exhibit this phenomenon.
The pancreas and salivary glands yield a little without breaking, when
they are pulled; but it is not their texture which is the seat of this
phenomenon, it is the abundant cellular texture that penetrates them;
thus their different lobes are then separated, in proportion as the
filaments which are between them become longer.

The glandular texture, which is very commonly called parenchyma, is in
general arranged in three different ways. 1st. In the pancreas, the
salivary and lachrymal glands, there are distinct lobes, separated by
cellular texture, resulting from smaller lobes which are agglomerated
together and which are composed of still less lobes, that are called
glandular grains; the scalpel traces with ease the first, second, third
and even fourth divisions. 2d. In the liver and the kidneys there is
found no trace of the first of these divisions, of those into principal
and even secondary lobes. The glandular grains all in juxta-position,
having between them an equal quantity of cellular texture, a quantity
which is very small, as we shall see, present an uniform texture
without inequality, which is broken with ease, as I have said, and the
rupture of which exhibits species of granulations. 3d. The prostate,
the amygdalæ and all the mucous glands have a soft parenchyma, like
pulp, without the appearance of principal or secondary lobes, or
even glandular grains, not breaking, yielding much more under the
finger that compresses it, than that of the other glands. The simple
inspection of the glandular system is sufficient to enable any one to
perceive the triple difference which I have just pointed out, and which
is essential. The testicles and the mammæ have a peculiar texture which
cannot be referred to these differences.

Authors have been much occupied with the intimate structure of the
glands. Malpighi admitted that there were small bodies in them, which
he believed were formed of a peculiar nature. Ruysch determined that
they were all vascular. Let us neglect all these idle questions, in
which neither inspection nor experiment can guide us. Let us begin to
study anatomy where the organs can be subjected to our senses. The
exact progress of the sciences in this age is not accommodated to all
these hypotheses, which made general anatomy and physiology but a
frivolous romance in the last.

There is no doubt that the excretories communicate with the arteries
which penetrate the glands. Injections made in these escape with great
ease by the first, without there being any trace of extravasation
in the gland. The blood flows often naturally by the excretories,
and produces sometimes bloody urine, saliva, &c. But do these facts
prove that there are only vessels in the glands, that the peculiar
parenchyma of which they are the result does not depend on a substance
which is peculiar to them? The glands, like all the other organs, as
the muscles, the bones, the mucous membranes, &c. have their peculiar
texture which especially characterizes them, which belongs only to
them, a texture in which the arteries communicate with the veins and
the excretories. Let us not push our researches further; if we do, we
shall be inevitably entangled in conjectures. Let us confine ourselves
to examining what phenomena distinguish this texture from all the
others when subjected to the different reagents. It is much to know
the characteristic attributes of the glandular system, without seeking
to understand its intimate nature, which, like that of all the other
systems, is concealed by an impenetrable veil.

The glandular parenchyma dried in the air after having been cut in
slices, loses its original colour, takes a deep one, black even in the
liver and the kidneys, in which it is owing especially to the blood
which penetrates these glands, since if they are dried after having
been deprived of it by repeated washing, they remain grey after their
drying. No system becomes harder or more brittle than this by this
preparation. It diminishes then less in size than most of the others.
When immersed in water after being thus dried, it becomes soft, resumes
in part its original appearance and its tendency to putrefaction, which
takes place immediately if it is left in the open air.

The glandular texture, when exposed to the air so that it does not dry,
becomes putrid very quickly, and gives out an odour more fetid than
most of the others. More ammonia appears to be disengaged from it. The
liver especially produces an insupportable odour when putrid. I do not
know any organ, kept in a vessel full of water to macerate, which gives
out more disagreeable emanations. The kidney becomes putrid much less
quickly; this varies however a little.

When boiled, the glandular texture furnishes in the first moments of
ebullition, a great quantity of grey substance, which mixes at first
perfectly with the water which it renders turbid and then collects
into a copious scum on the top of this fluid. It is this texture,
the fleshy, the mucous and the cellular which give the most scum in
boiling, as it is the cartilaginous, the tendinous, the aponeurotic,
the fibro-cartilaginous, &c. which give the least of it. It should not
be believed, moreover, that this first product of stewing is uniform in
its nature; it varies in each system in quality as well as quantity. At
least I have observed that its appearance is never the same, that it
has nothing constant but its frothy state, which also varies much and
which is even almost always nothing in the mucous system.

The liquor which results from the boiling is very much changed in
colour, and appears to contain many more principles than that made with
the white organs. An accurate analysis of the liquor in which each
system had been boiled would be an interesting subject of research. I
have found that in almost all the appearance, the taste and the colour
were different.

The glands exhibit a phenomenon when cooking that especially
distinguishes them. They harden at the moment of the first ebullition,
and acquire the horny hardness like all the other systems; but whilst
most of these soften again from long-continued stewing, so as to become
pulpy, the glands uniformly become harder, so that after five or six
hours boiling, they are three or four times as hard as they naturally
are. I have very often made this experiment, which is also well known
in our kitchens, in which when a gland is cooked, care is taken that
the stewing should not continue too long. Beef kidney finally becomes
soft; those of sheep and of man remain hard for a much longer time.
They soften however more than the texture of the liver, which is of all
the glands that which exhibits the hardness in the greatest degree.

Another phenomenon which especially distinguishes the ebullition of
the glandular system, is that when it is taken out at the moment
it has undergone the sudden horny hardening, common to almost all
the animal solids plunged into boiling water, it has not like the
others acquired elasticity. Draw in an opposite direction a tendon, a
serous or mucous membrane or a muscle that have undergone the horny
hardening, they stretch and afterwards suddenly contract the instant
the extension ceases; on the contrary, a slice of liver that has the
horny hardness breaks when it is drawn and never contracts. The texture
of the prostate appears to be more capable of then acquiring a little
elasticity. The non-fibrous disposition of the glands seems to have
much influence upon this phenomenon.

Exposed to the sudden action of a very bright fire as in roasting,
the texture of the liver and the other glands crisps and contracts on
the exterior. There results from it on the surface a kind of covering
impermeable in part to the juices contained in the organ, which in this
way becomes cooked in these juices which soften it in the interior.
This phenomenon is however common to all the solids. Hence why care is
taken to expose what is roasting, whether it be muscular or glandular,
at first to the action of a very quick fire; afterwards when the horny
hardening of the surface has been produced, it is diminished, and the
organ is cooked with a small fire.

The glands macerated in water yield differently to its action. The
liver resists it longer than the kidney, which after an experiment
of two months made in vessels placed in a cellar has been reduced to
a reddish jelly swimming in the water; whilst the first preserved
for the same time and a little longer, its form and density, and had
only changed its red colour to a blueish brown, whereas the kidney
retains its colour in maceration. The salivary glands contain much of
this white, unctuous and hard substance, which all the cellular parts
when long macerated exhibit. It is not the glandular texture that has
changed, but only the fat contained in the cellular texture, which is
here very abundant.

The acids act upon the glandular texture nearly the same as upon all
the others. They reduce them to a pulp which varies in its colour and
the rapidity of its formation, according to the acid employed. The
sulphuric is uniformly the most efficacious in producing this pulp
which it blackens, whilst the nitric yellows it. All the acids act with
much more difficulty upon the glandular texture when stewed, than when
raw. My experiments have convinced me that but few systems exhibit this
difference in a more remarkable manner.

The glands are much less digestible than many other animal substances,
especially when stewed, which produces in them in this respect an
effect entirely different from what it does in the cartilages, the
tendons, and all the fibrous organs, which by it lose their density,
become soft, gelatinous, viscid even and are easier dissolved by the
gastric juice. I believe in general that we should digest the glands
much easier by eating them raw. Every one knows that the more the liver
is cooked, the more indigestible it becomes. This induced me to make a
comparative experiment upon this organ cooked and raw; when one portion
in the second state was reduced to a pulp in the stomach of a dog, the
other portion in the first state swallowed at the same time had just
begun to be altered.


_Of the Excretories, of their Origin, of their Divisions, &c. Of the
Glandular Reservoirs._

All the glands have ducts destined to carry off the fluid which they
secrete from the mass of blood; now as they are only found in the
glands, they should be considered with the peculiar texture of these
organs. The origin of these ducts is uniform in all the glands. They
arise, like the veins, by an infinite number of capillaries, which form
the last ramifications of a kind of tree, these ramifications appear to
begin at each glandular grain, where these grains exist; so that for
each there is one of these, an artery and a vein. Arising thus from the
whole of the interior of the gland, these ducts soon unite and form
larger ducts, which usually go in a straight line though the glandular
texture, converge towards each other, unite with other ducts still
larger and terminate differently.

In respect to this termination, glands should be divided into three
classes. 1st. Some transmit their fluids by many ducts, each of which
is the assemblage of smaller ducts, opening at the side of each other,
but all entirely distinct and without communication. Sometimes at
the place where these ducts terminate, a more or less considerable
prominence is observed, as on the breast, as also on the prostate,
of which the verumontanum is a kind of nipple. Sometimes there is
a depression, a sort of cul-de-sac which is found at the place of
these orifices, as in the amygdalæ, upon the tongue, &c. Sometimes
the surface on which the different ducts of a gland open, is smooth
and even, as is the case with that on which those of the lachrymal,
sublingual and almost all the mucous glands open. 2d. Other glands
pour out their fluid by a single duct, as the parotids, the pancreas,
the sublinguals, &c. this arrangement is only a modification of the
preceding; where the duct opens, no inequality is usually discovered,
the surface is smooth. 3d. There are glands which, before throwing
out their fluid by their excretories, deposit it for some time in a
reservoir where it remains to be afterwards expelled; such as the
kidneys, the liver, the testicles, &c. Here there are always two
excretories, one which goes from the gland to the reservoir, the other
from the reservoir outwards. These reservoirs are evidently a part of
the same system to which their excretory ducts belong.

Though the first and second species of glands have no reservoir, yet
the different ramifications of their excretories may to a certain
extent be considered as such. In fact, these ramifications, as well as
those of the excretories of the glands with a reservoir, are constantly
full of the fluid which is secreted in these organs. Whatever may have
been the kind of death, the fluid of the prostate may be always made
to ooze out, by compressing the gland; I have often even by pressure
produced a very evident jet. The papillæ of the kidney also uniformly
give out urine when pressed. The liver cut in slices allows natural
bile to escape from the divisions of the hepatic duct. The semen is
uniformly found in the windings of the vas deferens. The lactiferous
vessels keep the milk in their cavity, till it is evacuated, and it has
even no other reservoir. The greater or less size of the mammæ during
lactation is owing to the greater or less fulness of these vessels. It
is also to this circumstance that must be referred the peculiar taste
of each glandular texture, which always borrows some sapid particles
from the fluid it secretes. We know that the kidney has always an
urinous odour, especially in old animals. It is to this also that I
refer the difference of putrefaction which I have observed between
this organ and the liver. We know that the bile undergoes putrid
fermentation sooner than the urine; this, when it is very acid, can
even preserve it to a certain extent from putrefaction; expose then
the liver and the kidney to it, the latter will almost always be the
last to become putrid, as I have said.

It appears in general that the course of the fluids in the excretories
is much less rapid than that of the blood in the veins and even than
that of the lymph in the absorbents; the following considerations place
this beyond a doubt. The urine flows continually by the ureters, as is
evidently proved by fistulas in the loins; now, in the time taken to
fill the bladder by this uninterrupted flowing, there would flow from a
vein of a diameter equal to that of the ureter ten times as much blood,
and much more lymph from the thoracic duct. Yet this rapidity of motion
is subject to many varieties; during the period of inactivity of the
glands, it is not half as great as during their activity; the salivary
fistulas are a proof of this. We know how promptly the ureters transmit
the urine from the drinks that are taken.


_Size, Direction and Termination of the Excretories._

The size of the excretories varies. 1st. Those which go out in
considerable number from a gland are very small, often hardly
perceptible. They commonly run their course in a straight line, do not
anastomose with each other and open immediately upon going out of the
gland. 2d. Those that are single are larger, always in proportion to
the size of their gland, except however the hepatic which is evidently
very small in comparison with the liver. They run their course out of
their glands, and arise from ducts as large as those of the preceding
ones; so that if a single trunk arose from the excretories of these,
they would resemble the others in every respect. They differ only in
this, that their secondary excretories open directly on their surface,
whereas they unite in a common trunk in the others. The pancreas is
the only one in which this common trunk goes concealed in the gland
itself. It is only in the testicles that it is tortuous, and in which,
on this account, it is longer than the course which it has to run.

Whatever may be their arrangement, the excretories pour all their fluid
either on the exterior, as the urethra, and ureters, the lactiferous
tubes, and the ducts of the sebaceous glands; or on the interior of the
mucous membranes, as the mucous, salivary, pancreatic, prostate and
hepatic excretories. The cutaneous and mucous surfaces are the only
ones then on which the excretories terminate, the only ones which their
fluids moisten. These ducts are never seen opening upon the serous or
synovial surfaces. The excretories of the pretended articular glands
would be, if they existed, an exception to the laws of the general
organization. The excretories never open in the cellular texture; if
this happens preternaturally, either abscesses take place from the
irritation which results from it, as in urinary fistulas, or a callus
forms in the course of the excreted fluid, and thus defend the cellular
system from a troublesome infiltration.

Hence the mucous tube of the intestines should be considered as a kind
of general excretory added to the pancreatic, hepatic excretories,
&c. and which throws out all the fluids which are separately poured
by these ducts into it. In fact, all the secreted fluids appear to be
destined, as I have said, to be thrown out of the body. Separated from
the mass of blood, they are foreign to it, and do not enter it in a
natural state. Though still contained in cavities with mucous surfaces,
they may be truly considered as being out of our parts. These surfaces
are really true internal integuments, destined to defend the organs
from the contact of the substances which they contain, a contact which
would inevitably be injurious to them.


_Remarks on the Secreted Fluids._

The fact that the secreted fluids are destined to be thrown out, a
fact which is incontestable with regard to the urine, the bile which
colours the excrements, the saliva, &c. has made me for a long time
believe that the introduction of these fluids into the sanguineous
system, would produce the most serious consequences. I was besides
confirmed in this, 1st, by my experiments, in which I have always seen,
as I have said, the urine, the bile, &c. injected into the cellular
texture, remain without being absorbed, but producing abscesses; 2d,
by the infiltration of the urine in the neighbourhood of the bladder,
from which abscesses always arise; 3d, by the serious consequences
from the effusions of this fluid in the peritoneum from the high
operation for the stone, and of the bile on the same surface in certain
penetrating wounds, in both these cases these fluids never re-enter
the blood by way of absorption, like the peritoneal serum, but almost
always occasion death; 4th, by an experiment in which I had seen a dog
die shortly after the injection of urine into the jugular. All these
considerations made me suspect that the secreted fluids, introduced
again into the mass of blood, were always fatal at the end of some
time, and that, as some physicians whose opinion is of great weight
have thought, all that has been said of the bile’s being poured into
the blood in bilious diseases, is but a consequence of vague ideas of
the reality of which there is no proof. Yet the importance of this
question, in regard to medical theories, has induced me to resolve it
by experiments, so as to leave no doubt upon the subject.

I have then injected into the jugular veins of many dogs bile taken
from the gall-bladder of other dogs which I opened at the same time.
For the first few days they appeared to be weary, did not eat, were
much altered, their eyes were heavy, and they were constantly lying
down; but after some time they gradually regained their former vigour.
I afterwards employed human bile in these experiments; the result was
the same, except that many times, the animal had hiccough and vomiting
some time after the injection. In one instance a dog died in three
hours after the experiment; but it was because I made use of that
extremely black fluid that is sometimes found in the gall-bladder
instead of bile which resembles thick ink, and which appears to form a
considerable part of those black vomitings that sometimes take place.

These experiments induced me to try some with the saliva, and I
obtained the same result from them; only the languid state that
succeeded the injection was less evident. I afterwards made use of
nasal mucus suspended in a sufficient quantity of water, for it
can hardly be dissolved in it. Finally urine itself was many times
injected, not that which comes immediately from drink and is only
aqueous, but that which is of slow formation. In this experiment the
dogs have been sicker, but only one died, and that happened on the
seventh day. I have many times repeated it, on account of that which
I performed three years ago; the same result has always taken place,
which makes me think that being but little used at that time to make
experiments, I introduced by accident a bubble of air through the
syringe, which is sufficient to produce the death of the animal.

A question then is evidently settled by the experiment. The secreted
fluids, though destined to be thrown out in the natural state, can
re-enter the circulation, without causing the death of the animal,
which is only more or less affected according to the nature of the
fluid injected. Whether the bile circulates or not with the blood in
bilious fevers, I have not examined; but it certainly can circulate
with it after having been absorbed in its canals. I do not doubt
but that in purulent reabsorptions, the pus circulates in its
natural state in the sanguineous system; I confess that I have not
made experiments upon the injection of this fluid, but I intend to
immediately.

We exaggerate every thing. No doubt the solids in which the vital
forces are especially inherent, are particularly affected in diseases;
but why should not the fluids be affected also? Why should we not seek
in them causes of disease as well as in the solids?

There are cases in which these are primarily affected, and in which the
fluids are so in consequence; thus in cancer, in the affections of the
liver, the spleen, &c. in most organic lesions, the various yellowish,
grey, brown and even greenish shades of the face, are an index of the
consecutive alterations which the fluids experience in their colour and
consequently in their nature.

In other cases the affection commences with them; as when the venom of
the viper is introduced into the blood, as when reabsorption of pus
takes place from external abscesses, or in phthisis, and as when there
is absorption of various contagious principles. There is no doubt that
the different substances which can be introduced with the chyle into
the blood, may be the cause of various diseases. Is it not the blood
which carries to the brain the narcotic principles which produce sleep?
does it not carry turpentine and cantharides to the kidneys, mercury to
the salivary glands, &c.? Inject opium, wine, &c. into the veins, and
you will stupify the animal the same as if you had given them by the
stomach.

Physiologists at one time were much engaged with the introduction of
medicinal infusions into the veins of living animals. They circulated
by these infusions purgatives, emetics and a thousand other foreign
substances, the contact of which the blood bore, without occasioning
any other accident to the animal than that of vomiting or alvine
evacuations if they were emetics or purgatives, and a greater or less
general derangement if they were other foreign substances which had no
affinity with any particular organ.

The caustics, as the nitric and sulphuric acids and other very
irritating substances, have alone caused death in these curious
experiments of which Haller has given us a sketch, and which prove that
various substances wholly foreign to the blood can circulate in it, and
that it is a common mass in which are found many principles differing
from each other, and which cannot be always essentially the same. In
these experiments the most important part has been neglected, that of
the infusion of the different animal fluids, particularly the secreted
ones, and those also which are preternaturally produced in diseases. I
think that the different reabsorptions would be much elucidated by the
infusion of the various kinds of pus, sanies, &c. But we have already
sufficient facts to convince us that the fluids and especially the
blood can be diseased; that the various foreign substances mixed with
it can act in a fatal manner upon the solids. In fact, every acrid,
irritating matter, without being mortal, accelerates the action of the
heart and produces a true fever, if injected into the veins. In all
these cases, it is always necessary that the solids should act; for
all the morbid phenomena suppose their alterations; but the principle
of these alterations is in the fluids. They are the excitants, and the
solids the organs excited. Now if there are no excitants, there is no
excitement, and the solids remain unaffected.

Finally there are cases in which the whole economy both solids and
fluids seem to be simultaneously affected; such are adynamic fevers,
in which at the same time that there is a general prostration of the
first, the second appear to be really decomposed.

Let us not exaggerate then medical theories; let us regard nature in
diseases as she is in a state of health, in which the solids elaborate
the fluids and are at the same time excited by them. There is a
reciprocal action, every thing succeeds each other, every thing is
connected together. Our abstractions hardly ever exist in nature. We
usually adopt a certain number of general principles in medicine, and
we accustom ourselves afterwards to deduce from these principles, as
necessary consequences, all the explanations of diseases. There is in
physical phenomena a regularity and uniformity which never deceive. In
morals even, there is a certain number of principles acknowledged by
all men, which direct them and regulate their actions; hence a constant
uniformity in our manner of considering moral and physical phenomena;
hence the habit of going always from the same principles in reasoning
upon them. We have carried this habit into the study of the living
economy, without considering that it incessantly varies its phenomena,
that under the same circumstances they are hardly ever the same, that
they are continually increased and diminished and have a thousand
different modifications. Nature seems at every instant to be irregular,
capricious and inconsequent in their production, because the essence of
the laws which preside over these phenomena, is not the same as that of
the physical laws.

I would observe that the experiments the result of which I have just
given for the secreted fluids, differ from those which I published
the last year, and in which these fluids have always been fatal, the
instant they were forced towards the brain by the carotid. This is a
phenomenon general to all the irritating fluids, whether drawn from the
economy, or foreign to it; they destroy life when they arrive at the
cerebral organ, by a direct injection and without having undergone any
alteration, whilst we can inject them with impunity into the veins,
as the experiments of the physicians of the last age have proved. We
can even without danger, as I have observed, introduce them into the
arterial system, on the side opposite to the brain, as in the crural
artery, for example. Do the fluids mixed with the black blood rid
themselves of some principles by respiration, before they arrive at the
brain, or is the preceding phenomenon owing to other causes? I know
not. I would only observe that every thing which is not arterial blood,
as the black blood and even serum, produces death when forced into the
carotid. Water alone is injected with impunity. When the irritating
principles are much diluted in this fluid, their contact is less
injurious. I have seen very light coloured urine not produce death.


_Structure of the Excretories._

All the excretories have an internal membrane which is mucous, and
which is a continuation of the mucous or cutaneous surfaces, upon which
they terminate. But besides this, they all exhibit an external covering
which forms the shell, as it were, of this mucous canal. This shell
is very thick in the vas deferens, in which it exhibits a texture but
little known. In the urethra it is of a spongy nature, containing much
blood and analogous to the glans of which it is a continuation. In the
ureters, in the hepatic, salivary ducts, &c. it is this extremely dense
and compact cellular texture of which we have spoken, which, by its
structure, resembles that of the arterial and venous cellular texture,
and which differs essentially from the ordinary cellular texture, as
from the intermuscular. It does not appear that there is in these ducts
a membrane differing from this dense texture and the mucous surface.

Each excretory has its vessels. The ureters evidently receive branches
from the renal, spermatic arteries, &c. &c. The hepatic gives them to
the ductus choledochus; the transverse artery of the face supplies
the duct of Steno. Various nerves coming from the ganglions accompany
the corresponding arteries and veins. Yet I have uniformly observed
that there is never around these ducts a plexus as evident as there is
around most of the arteries.

The excretories have principally the vital properties of the mucous
system which forms them in great part. Their sympathies are also nearly
of the same nature.


II. _Parts common to the Organization of the Glandular System. Cellular
Texture._

The glands differ much in the cellular texture which enters into their
structure. We may even, in this respect, divide them into two classes.

In all the salivary glands, in the lachrymal, in the pancreas, in all
the glands with a granulated and white parenchyma, it is very abundant.
Each glandular body is divided into lobes very distinctly separated
by grooves which this texture fills, and which produce the lobulated
appearance on the exterior of this species of gland; not only each
lobe, but each lobule, each glandular grain even, has also the cellular
texture for a boundary. In this respect, this sort of gland is truly
an assemblage of small distinct bodies, which, separated from each
other, would also perform well their functions. This is what is seen
in the parotids, in which different accessory glands are often found
in the course of the duct of Steno, and are perfectly independent of
the principal gland. Sometimes there is a continuity, sometimes there
is a separation between the sub-maxillary and the sub-lingual glands.
The cellular texture is often loaded with much fat in this species of
gland. This is especially remarkable in the mammæ, the size of which is
owing sometimes to the glandular texture, as in young people in whom
this texture predominates over the fat; sometimes to the predominance
of this fat, as we see after the fortieth year, when this gland
preserves a considerable size. The difference is easily perceived by
the touch by the softness and flaccidity of the organ in the second
case, and by its resistance and firmness in the first. In the age of
puberty often, it is also the fatty cellular texture which increases
the size of this organ. Hence why there is often but little milk from
a large breast, and a much greater quantity from a smaller one. In the
voluptuous sensations which we experience at the sight of this organ,
we distinguish very well, without being conscious of it, the breast
whose prominence is real, from that which is not, and in which the fat
only raises the skin of the breast. It is rare in the salivary glands,
the pancreas, &c. that the cellular texture predominates so much, that
the fat accumulates in them in so considerable a quantity. I have
however seen cases in which the parotid resembled a fatty muscle; but
there was no increase of size.

In the testicle, whose parenchymatous portions are separated as in the
preceding glands, the cellular texture is not the medium of union.
There is found between each grain species of threads which appear to be
excretories, and not real cellular laminæ.

In the glands with a compact parenchyma, as the liver, the kidney, the
prostate, the mucous glands, &c. &c. there is very little cellular
texture; by tearing them in different directions, they break without
exhibiting intermediate laminæ. Fat is never found accumulated in
their parenchyma. The fatty state of the liver which takes place in
many diseases, and which is not, as has been thought, an affection
necessarily attendant upon phthisis, exhibits a phenomenon wholly
different from the mammæ and the salivary glands when they have become
fatty. The fat enters then like an element into the texture of the
organ; it is in this respect like the colouring substance, whose place
it has as it were taken; it is not found in cells. Moreover much of
it can be extracted by ebullition, and I have observed that much of
it swims on the surface of the water in which livers of this kind are
boiled. The kidney also has fat in its interior; but it is around the
pelvis and not in its peculiar parenchyma. The amygdalæ, the prostate,
the mucous glands, &c. never have it. Serum is never effused into the
texture of the glands with a compact parenchyma. The most complete
leucophlegmasia leaves them sound in this respect.

Yet it cannot be doubted that the cellular texture exists in these
glands; maceration demonstrates it in them. In the fungous tumours
that grow out of them, there is much of it. It is principally around
the vessels that it is found; the capsule of Glisson is an example of
this. It often happens even, as I have been led to observe, that this
texture becomes diseased, whilst that of the gland remains sound. Thus
we see steatomatous tumours developed in the liver, serous cysts in the
kidney, hydatids in both, and various productions in the other glands,
without deranging the secretion in the least. It is upon the liver
especially that these observations are best made; its size is trebled,
even often quadrupled by internal tumours, without an increase of its
texture; this texture dilated forms between these tumours, species of
partitions in which the bile is secreted as usual. The same thing takes
place in the kidney, in which serous cysts are found. Sometimes these
cysts grow there till the whole glandular texture is destroyed, and
there remains only a large sac separated by membranous partitions, and
filled with serum. I have preserved three kidneys of this kind.


_Blood Vessels._

All the glands not covered by a membrane, receive their arteries from
all sides. Numerous branches coming from the neighbouring vessels,
penetrate the whole surface of the pancreas, the salivary and lachrymal
glands, &c. These arteries wind at first in the interstices between
the lobes, ramify afterwards between the smaller lobes and finally
penetrate the glandular grains. Each of them has its own artery;
all communicate together; so that those of the sub-maxillary and the
sub-lingual are filled by injection made by means of small tubes into
the sub-mental, the external maxillary or the lingual, as well as by an
injection of the trunk even of the external carotid.

In the glands surrounded by a membrane, as the liver, the kidney,
the testicle, &c. the arteries enter only at one side, usually in a
fissure, and by a single trunk which is very considerable, and which is
sometimes divided into many branches more or less large. This part of
the gland in which the artery enters is always the most distant from
the action of external bodies, a remark common to all the important
organs, as the lungs, the intestines, the spleen, &c. which always
present externally their convex surface, that on which the vessels are
the most ramified; so that the place where an injury can happen to
them is that where hemorrhage is the least to be feared. The principal
artery, after it has entered the gland, is soon divided into different
branches which separate and are subdivided as they approach the
convexity. They give off in their course many branches to the body of
the gland and then terminate by a great number of capillaries on the
convex part of the gland. They often even pierce the organ and ramify
between it and the membrane which covers it. For example, by injecting
the hepatic artery, if the liver is bare, many small blackish striæ
suddenly appear on its convexity, which are owing to this cause. The
best means of seeing the glandular arterial system, is to inject a
kidney with a solid substance, and afterwards destroy its parenchyma
by maceration or something else. The arterial system is then bare and
entirely by itself. Many of these preparations are found in anatomical
museums.

The great arterial trunks winding in the glands, communicate to them
an internal motion very favourable to their functions. This motion is
so much the more evident, as almost all these organs very near the
heart by their position in the trunk, are, if we may so say, under the
immediate jar of its contractions. The salivary glands, the mucous
ones of the mouth and the lachrymal on the one hand, the testicle,
the prostate and the mucous ones of the genital parts on the other,
exhibit the extremes of this position. Another cause which favours the
jar of the glands by the entrance of the blood, is that almost all
the arteries that go to them run but a very short course before they
enter them. The spermatic alone is an exception to this rule; thus,
every thing in the secretion of semen seems to be characterized by a
remarkable slowness. To this constant motion imparted to the glands by
the entrance of the blood, should be added that which is communicated
to them by the neighbouring organs, and which keeps them in a constant
excitement, which is more necessary to their secretion than to their
excretion. In considering the action of organs, the constant motions
with which they are agitated has been too much neglected. The example
of the brain ought however to fix the attention of physiologists upon
this point.

The veins, everywhere continuous with the arteries, follow the same
distribution in the glandular system, and accompany them almost
everywhere. We do not see superficial and deep-seated veins, as we do
in many other organs. The liver is the only example in which the red
blood enters at one side, and the black goes out at the opposite.

Most of the veins of the glandular system pour their blood into the
general system of black blood, and as many glands are very near the
heart, they feel the reflux which this system often experiences. This
phenomenon is particularly remarkable in the liver, as the hepatic
veins open but very little below the right auricle. Hence why whenever
this auricle is considerably distended, as in asphyxia and in death in
which the lungs being crowded present an obstacle to the blood, the
liver has a much greater quantity than usual. I have uniformly made
this observation. Weigh comparatively this organ when the auricle is
full and when it is empty in the dead body, after having first tied
all its vessels; you will find a very great difference. For the same
reason, you will observe a constant relation between the weight of the
liver and that of the lungs, provided a morbid alteration of texture
of one of them be not the cause of death. The veins of many glands, as
those of the mucous ones of the stomach and the intestines, as those of
the prostate, &c. pour their blood into the system of abdominal black
blood. There are hardly any in the system of which we are treating, but
these veins, those especially of the glands situated in the pelvis,
which become varicose. Varices of the prostate are frequent, as we know.


_Of the Blood of the Glands._

The quantity of blood that is constantly found in the glands varies
remarkably; they may even be divided in this respect into three
classes. 1st. In the pancreas, the salivary, lachrymal glands, &c.
there is found but very little. It does not furnish the colouring
matter to these organs, which are white, and which, when macerated,
tinge with red but two or three waters. 2d. In the mucous glands, the
prostate, the testicles, and the amygdalæ, there is found a little
more. 3d. The liver and the kidneys contain so great a quantity of
it, that there is not in this respect any proportion between them and
the rest of the glandular system. This is owing in a small degree in
the first to the cause pointed out above; thus it often contains more
than the second, but it is not the essential cause. After death by
hemorrhage in which there was no reflux, in the liver or the kidney
suddenly taken from a living animal, &c. we observe the same thing. In
macerating these glands, it is necessary to renew the water at least
a dozen times before it ceases to be bloody. Hence why when they are
preserved in alkohol on account of an organic disease of which they
were the seat, they must be first macerated for a long time; if not,
the liquor soon becomes turbid from the blood. It is this quantity of
blood which gives to these glands a greater weight in proportion than
that of the other parts. It is from this that their redness is derived,
a colour which no other part exhibits to the same degree, but which is
not more strongly inherent in their texture, than it is in the mucous
surfaces or the muscles. In fact, we remove it with the same ease by
repeated washing. Then the liver assumes a greyish appearance, which
appears to be the colour inherent in its texture, as white is that of
the fleshy fibre. The kidney seems a little less to derive its colour
from the blood. It remains in part red when macerated; the pulp even
which is the product of it, after remaining some months in water, that
has been often changed, still exhibits in some degree this colour, much
less however than in a natural state.

Does the state of the secretions make the quantity of the glandular
blood vary? Does more of this fluid enter the kidney when it furnishes
much urine, than when it secretes but little, or if the same quantity
is brought by the arteries, is less returned by the veins in the first
than the second case? This is an interesting subject for experiment.

Is the nature of the blood changed when it arrives at the glands? Has
it a peculiar composition before entering each of them? Much has been
said of this change necessary to secretion; but that this may take
place, there must be a cause to produce it; now what is this cause
here? Does not the blood circulate in the trunks which go to the
glands, as in the others? It would be necessary then that the gland
should be surrounded with an atmosphere which acts upon the blood at
a certain distance from the place where it is; a vague idea, which
has no solid foundation, and which is met with only in the books of
those who have never made experiments. I have drawn blood from the
carotid, spermatic, hepatic and renal arteries; it is equally red and
coagulable. In the same animal, it is impossible for the senses to
discover the least difference.

I would observe that secretion differs essentially from nutrition in
this, that it always draws the materials of its fluids from the red
blood, whereas the second often takes its own from the white fluids, as
we see in the tendons, the cartilages, the hair, &c.


_Nerves._

The glands receive two species of nerves. 1st. The cerebral are found
almost exclusively in the salivary and lachrymal glands, the amygdalæ,
&c. 2d. The testicles, the prostate gland and the liver receive them in
an almost equal proportion from the brain and the ganglions. 3d. The
kidneys and most of the mucous glands receive scarcely any but those
of the ganglions. What is now said of the nerves should be understood
only of those that are free and independent of the arteries; for each
arterial trunk that enters a gland, is surrounded by a nervous net-work
belonging to the system of the ganglions, which is very evident in the
great glands, as in the liver and the kidneys where this net-work comes
from the semilunar ganglion, in the salivary glands where it comes from
the superior cervical, in the testicles where it comes from the lumbar
ganglions, &c.

Compared with the size of the glands, the nerves are in small
proportion, notwithstanding what Bordeu has said. It is not necessary
in fact to judge of this proportion by those of the parotid and
sub-maxillary glands, which merely pass through these glands without
stopping in them, and leave only some branches there. For example,
there is certainly no organ in the economy, among those which receive
nerves, that, in proportion to its size, has so few as the liver.

Besides, the nerves enter the glands nearly in the same way as the
blood-vessels, that is to say, 1st, on all sides, in those that have no
membrane; 2d, by a groove only in those that are covered with one. They
divide and subdivide after entering it, and are soon lost sight of.
Ganglions never exist in the interior of the glands.

Have the nerves an influence upon secretion? It is probable they have,
as every gland is provided with them; but they by no means exert so
immediate an influence upon this function as many physicians have
pretended. 1st. It is said that the nerves of the parotid glands have
been cut, and that the secretion of the saliva has been suppressed.
This division is evidently impossible, since the gland must be
extirpated before removing its nerves. 2d. I have divided the nerves
of the testicle of a dog, the only gland in which this experiment can
be made. I could not obtain any result, because an inflammation of the
gland came on and it suppurated; but this suppuration even supposes
that the nervous influx is not actually necessary for secretion,
since suppuration is accomplished by a mechanism analogous to that of
this function. All physicians know that a paralyzed limb can inflame
and suppurate. 3d. Erection and the ejection of semen take place in
paralysis of the lower half of the body, in which at least the nerves
of the prostate gland are completely paralyzed. Mr. Ivan related to me
the case of a soldier who took gonorrhœa in this state. 4th. We know
that when the bladder is perfectly paralyzed and its nerves have no
longer any action, its mucous glands still continue to secrete their
fluid so as even to produce a catarrh. 5th. The nostril of the affected
side in hemiplegia is as moist as usual. The ear of this side has its
ordinary quantity of wax. 6th. In paralysis of the uvula, the action of
its glands continues. 7th. When the eighth pair of one side of a dog
is cut, the bronchia is found some days after to contain as much mucus
as common. 8th. During the convulsions of the different parts in which
there are glands, and when consequently the nerves of these glands are
more excited, their secretion is not increased. 9th. If we weigh the
proofs given by Bordeu of the influence of the nerves on secretions,
we shall see, that they either rest upon false facts, like those of
the section of the nerve, of sleep, &c. or upon vague data. In general
physicians attach no precise idea to the term _nervous influence_;
the habit of experimenting shows how much they have abused it. When a
nerve being cut, paralyzed or irritated in any manner, the organ which
receives it undergoes no derangement in its functions, we certainly
are unable to appreciate the nervous influence upon this organ. I do
not say that it does not exist, but I maintain that we know nothing
about it, and that we ought not to employ at hazard a word to which
we cannot attach any precise idea. What word will you employ then to
express the influence of the nerves upon the organs of the senses, upon
the voluntary muscles, &c. if the same one is used to express an action
which has no relation with this, and which perhaps even does not exist?


_Exhalants and Absorbents._

This kind of vessels is but little known in the interior of the glands,
where they perform only the purposes of nutrition.


ARTICLE THIRD.

PROPERTIES OF THE GLANDULAR SYSTEM.


I. _Properties of Texture._

These properties are in general very inconsiderable in this system,
which appears to me to be particularly owing to its non-fibrous
texture. In fact, in order to be elongated and afterwards contracted
and preserve their integrity, it is necessary that the particles of an
organ should possess a certain degree of adhesion and cohesion; now, it
is to the fibre that especially belongs this double attribute. Observe
also that the glandular system is subjected to much less frequent
causes of distension and contraction, than the systems with distinct
fibres. It is scarcely ever found distended except when purulent
deposits, serous, steatomatous collections, &c. are formed in its
interior, as often happens in the middle of the liver, kidney, &c. now
in these cases it does not yield like the skin, the muscles, &c. its
particles are separated; it is the cellular texture with which they are
surrounded that is uniformly dilated; the glandular texture is even
soon destroyed. It is very evident when the collections are formed near
the convexity of the glands; if the tumour be at all large the texture
of the organ disappears; there remains only a cellular and membranous
cyst. Hydatids so frequent on the exterior of the kidneys present us
with examples of it. If it is in the middle of the gland that the
cyst is formed, the destruction also takes place, but it is much less
evident.

A strong proof of the small degree of extensibility of the glands, is
what takes place in the liver in dead bodies. I have said above that
it is more or less loaded with blood, according as the system with
black blood had been more or less embarrassed in the last moments. Now
whatever may be the quantity of blood it contains, its size remains
nearly the same; only its texture is more or less compressed by the
vessels, whilst on the contrary the greater or less size of the lungs,
which is very apparent, always indicates its state of fulness or
vacuity. It is probable even that it is this difference which has made
all physicians neglect the infinitely various states of engorgement
in which the liver may be found at death, whilst they have had a
particular regard to the varieties of the lungs.

The veins of the kidneys, further from the heart, are less exposed than
those of the liver to the reflux that takes place in the last moments
in which the black blood is obstructed in the lungs. Yet it however
takes place, and we see very great varieties in the quantity of blood
in the great renal vessels, a quantity independent of that which is
constantly found in the organ, and which, as I have said, is very
considerable. Now the size of the kidney hardly corresponds to these
varieties, because its extensibility is almost nothing.

As to the glands situated at the two extremities, as on the one
hand the testicles, and on the other the salivary glands, we hardly
observe in them the sanguineous stagnation, because the reflux is not
sufficiently evident. We cannot then, in this way, judge but by analogy
of their extensibility and contractility.

Yet the engorgements of the testicles, consequent upon gonorrhœa,
and the various swellings of the parotid glands prove that these
properties exist to a certain extent. Are the liver, the kidneys and
other internal glands subject to those acute swellings that are often
seen in the sub-cutaneous ones? It is very probable; perhaps even
physicians have not paid sufficient regard to the accessory symptoms
which may arise for a moment from the pressure of these swelled organs
on the neighbouring parts. Besides, this swelling and the contraction
that follows it, may take place especially in the cellular texture of
the gland, and consequently suppose less extensibility of the glandular
texture than they at first seem to.


II. _Vital Properties. Properties of Animal Life._

The animal contractility is evidently nothing in the glandular texture.
Does the sensibility of the same kind exist in it? The following facts
are connected with this. 1st. A compression of the parotid is to a
certain degree painful. I have even been obliged, in a particular case,
to give up the method of compression that Desault had advised for a
salivary fistula, on account of the pain the patient experienced; but
the numerous nerves which traverse this gland may be the cause of these
pains. 2d. We know that the instant the lithotome cuts the prostate,
or the stone and forceps pass over it, the patient suffers very much.
3d. Stones lodged in the kidneys occasion horrible pains. 4th. Any
considerable pressure of the testicle is very painful.

On the other hand we can cut the texture of the liver and the animal
will give no signs of pain. Haller, after many experiments, ranked the
glands among the insensible parts. What is to be concluded from this?
That the animal sensibility, modified in a thousand ways, appears
to exist in many organs in which certain agents cannot put it in
action, and in which others develop it remarkably. We know that the
various morbid alterations render it very evident in the glands. The
inflammatory pain of these organs has even a peculiar character; it
is obtuse and dull in the greatest number of cases. There is never
experienced in them the acute sensation which characterises cellular
inflammation, or the sharp and biting pain of which the skin is so
often the seat.


_Properties of Organic Life._

Of the properties of organic life, the sensible contractility is
wanting in the glandular system. But the two other properties are
developed in it to the highest degree. They are in constant activity;
secretion, excretion and nutrition keep them in incessant action there.
It is by its organic sensibility that the gland distinguishes, in the
mass of blood, the materials which are proper for its secretion. It is
by its insensible contractility, or its tonic forces, that it contracts
to throw out those which are foreign to this secretion. The first is on
a small scale in each gland, what the animal sensibility of the tongue
and the nostrils is on a large one, which allows only aliments suitable
for the stomach to be introduced into its cavity; the other does
insensibly, what is effected in so evident a manner by the glottis,
when it rises up convulsively against a foreign body that attempts to
enter it. The blood contains the materials of all the secretions, of
the nutrition of all the organs, and of all the exhalations. Each gland
draws from this common reservoir what is necessary to its secretion, as
each organ does what is proper for its nutrition, and as each serous
surface does what is suitable for its exhalation. Now it is by its
organic sensibility that each living part of the body distinguishes
what its functions require.

When the fluids enter the small vessels of the gland, this sensibility
is the sentinel that gives notice of it, and the insensible
contractility is the agent which opens or closes the gates of the
organ, according to the principles that are presented. This comparison,
if I may be allowed the use of it, gives an idea of what then takes
place. Every glandular action turns then especially upon these two
properties, and as this action is almost permanent, they are then
constantly in exercise.

From this it is evident, that all the glandular diseases ought to
suppose a derangement in these properties; for, as we have often seen,
they are the predominant properties of an organ, those, the exercise
of which constitutes its peculiar life, which especially determine its
diseases, by their alteration. This is in fact what observation shows
us. Here we see these properties increased or diminished, sometimes
produce an increase of secretion, as in diabetes, mercurial salivation,
immoderate flow of bile, &c. sometimes a diminution, a suspension
even of this function, as in acute diseases in which all the ducts are
closed as it were in a moment, as in the suppression of urine, dryness
of the mouth, &c. It is the alteration in the nature of the glandular
sensibility that puts it in relation with fluids foreign to the glands
in a natural state; hence the innumerable varieties of the secreted
fluids especially in diseases. I have spoken of these varieties as
it regards the mucous fluids. The liver and the kidneys particularly
do not experience less numerous ones. The taste, the colour, the
consistence and odour of cystic bile appear in a thousand different
states in dead bodies. Who is ignorant of the innumerable alterations
of which the urine is susceptible? The saliva is less variable; but in
diseases how different is it from its natural state. It is sufficient
to have noticed for some time the various evacuations in diseases, to
see of how many modifications they are capable. Nothing less resembles
the urine and bile, than the fluids sometimes thrown out by the bladder
and the liver; whence do these varieties arise? From this, that
the variable organic sensibility places the organ in relation with
substances to which it was foreign in a natural state; and from this,
that the insensible contractility allows substances to enter the organ
which it before excluded. The same gland without changing its texture,
by a modification only of its vital forces, can then be a source of an
infinite variety of different fluids; I believe even that the kidney,
by taking a sensibility analogous to that of the liver, may secrete
bile. Why may it not secrete it, if it can secrete other fluids so
different from its own?

In health, each gland has a mode of sensibility nearly uniform, a mode
which changes but little; thus each secreted fluid has an appearance,
a consistence and a nature always nearly the same. But in diseases,
a thousand causes change this mode at every instant. An hysterical
paroxysm strikes the kidneys; in an instant they repulse all the
principles that colour the urine, and this comes out limpid; the
paroxysm passes off, the organ resumes its ordinary sensibility, and
the urine returns to its usual state. The influence of the epileptic
paroxysm extends to the sensibility of the salivary glands; in a
moment, a thick, copious and frothy saliva, wholly different from the
natural, comes from the mouth; after the paroxysm, the sympathetic
storm is calmed in the gland, and the saliva returns to its ordinary
state. If I may be allowed the comparison, the glands are in diseases
like the atmosphere in the equinoxes. At these periods, the winds which
succeed each other and incessantly change, often make rain, hail and
snow succeed each other in a very short time; so the forces of the
glandular life, constantly variable in diseases, make the different
products of secretion vary with rapidity.

It is not only to secretion that the various alterations of the organic
sensibility and the insensible contractility of the glands extend;
these alterations when long continued, have an influence also upon
their nutrition; they disturb the course of it; hence the changes of
texture, the tumours of different kinds, the organic diseases, &c.
that are so frequent in the glandular system, a system which presents
the greatest field for morbid anatomy. The great number of organic
diseases which it exhibits, in our dissecting rooms, compared with most
of the other systems, is very striking. The glandular, the cutaneous,
the mucous, the serous, the cellular systems, &c. hold the first rank
in this respect. Observe also that it is in them that the organic
sensibility and the insensible contractility are raised to the highest
degree, because they are the only ones in which these properties are
brought into action not only by nutrition, but also by various other
functions that are going on in the insensible capillary system, viz. by
exhalation, absorption and secretion.


_Sympathies._

Few systems are more frequently the seat of sympathies than this. In
examining them I shall adopt the same order as in the preceding system.


_Passive Sympathies._

The glandular texture is affected with extreme ease by all the others.
This constitutes its passive sympathies. They take place, 1st, in a
natural state; 2d, in diseases.

I say first that there are certain cases in the natural state, in which
the other organs being excited, the glandular is brought into action.
This is especially remarkable in the mucous system. We have seen that
almost all the excretory ducts terminate upon the mucous surfaces.
Now when one of these surfaces is irritated in the neighbourhood of
an excretory duct, the gland of this duct increases its action. 1st.
The presence of aliments in the mouth produces an abundant flow of
saliva. 2d. A sound in the bladder, irritating the ureters or their
neighbourhood, increases the flow of urine. 3d. The irritation of the
glans penis and the extremity of the urethra in coition, produces a
kind of spasm in the testicle from which arises a copious secretion
of the seminal fluid. 4th. Every irritating fluid applied either to
the conjunctiva, or the pituitary membrane occasions a more or less
considerable flow of tears. 5th. By making experiments upon the state
of the gastric viscera during digestion and during hunger, I have
observed that as long as the aliments are only in the stomach, the flow
of bile is inconsiderable, but that this flow increases when they pass
into the duodenum, so that much of it is then found in the intestines.
During hunger, the gall-bladder is much distended; but little bile
flows from it. At the end or even during digestion, it contains but
half as much bile. Yet it might be emptied much more easily during
abstinence, as the fluid which is then found in it is of a deep green,
very bitter, very acrid and consequently very irritating. On the
contrary, during or immediately after digestion, it is much milder,
of a bright yellow and less irritating. There must then be another
stimulus for it during digestion; this stimulus is the food that is
passing by the extremity of the ductus choledochus. I have pointed
out in a long note in my Treatise on the Membranes, the course of the
cystic and hepatic bile.

Let us conclude from these numerous considerations, that one of the
principal means which nature employs to increase the action of the
glands, and to produce that of the excretory ducts is the sympathetic
irritation of the extremity of these ducts or of the neighbourhood of
the point of the mucous surface where they come out. It is to this also
that must be referred the various catarrhs produced by an irritating
body remaining upon one of these surfaces. The infant in sucking and
irritating the nipple, produces a secretion of milk at the same time
that he draws it out. In a morbid state the glands are also very
frequently the seat of passive sympathies. It is almost always then the
organic sensibility and the insensible contractility that are brought
into action in them. It is rare, that the animal sensibility, excited
by sympathies, occasions pains in the glands.

We have said that the varieties the glands exhibit in diseases are
innumerable, either as it respects the quantity or the quality of the
fluids they secrete. Now all these varieties are especially owing to
sympathetic influence. Observe the salivary glands moistening the mouth
or leaving it dry, filling it with a viscid or limpid fluid, frothy
or thin, the mucous glands of the tongue furnishing sometimes a thick
whitish substance, and sometimes a black crust. Physicians consider the
state of the tongue as a constant index of that of the stomach; this
is most often true. Nature has established such a sympathetic relation
between these two parts, that when the mucous surface of the stomach
is disordered, and is the seat of that kind of catarrh which is called
derangement, fulness of the stomach, &c. that of the tongue is also
affected and furnishes more mucous juices, which alter and destroy the
appetite, and thus prevent the taking of aliments which the stomach
could not digest, and which often even it would not bear. The tongue
is then, as in a state of health, a kind of sentinel placed over the
stomach, to refuse that which would injure, and to admit that which is
suitable for it. This is no doubt the cause of this singular influence
which the stomach exerts upon it in diseases. But let us also remark
that sometimes the tongue is foul, when the stomach is in the ordinary
state. This phenomenon is frequent in hospitals; it happens to me very
often. And vice versa, nausea, &c. sometimes takes place without a
catarrh of the tongue.

Shall I speak of the innumerable influences that the liver, the kidney
and the pancreas receive? When an organ is diseased in the animal
economy, these immediately perceive it; their secretion is increased,
diminished or altered, and oftentimes even the sympathetic affection
does not extend to these functions, but produces inflammation,
suppuration, &c. We know that abscesses are formed in the liver from
wounds in the head, &c. Shall I speak of the innumerable varieties of
the flowing of tears in acute diseases, in inflammatory and malignant
fevers, &c.? Who does not know that the eye is then more or less moist,
that it is often constantly weeping? Now whence arise these varieties?
from the sympathetic influence which the lachrymal gland receives. The
disease itself is often foreign to it; but the unknown consensus which
connects the glands with the diseased parts, makes them then enter into
action. We weep from a variety of passions, from grief especially; how
does this happen? Because the influence of the passion is first carried
to the epigastric region, as the violent sensation experienced there,
proves; and the affected organ reacts upon the lachrymal gland. We weep
in the same way as we sweat from fear, or spit copiously in anger, a
phenomenon which the vulgar express by these words, _foaming with rage_.

The testicles and the prostate are much less often sympathetically
influenced in diseases than the other glands. Whilst every thing is
disturbed in the glandular system, they most frequently remain calm
and tranquil. Why? because they are insulated by their functions from
the other glands. The salivary glands, the pancreas, the kidneys,
the liver and almost all the mucous glands contribute to one common
object, viz. digestion. This object is connected with the existence of
most of the other organs. When these are diseased, it is not wonderful
that the glands feel it. On the contrary, the testicles, destined only
to the purpose of generation, entering later into action and ceasing
to act sooner than the other glands, having great intermissions in
their action, cannot in their affections be thus connected with the
diseases of the other organs. Sometimes however they are. We know that
some affections of the lungs dispose to venereal pleasures; that in a
natural state, a lively excitement of certain parts of the skin, of
that of the glutæi muscles especially brings into activity the whole
genital system, &c. &c.

We know the remarkable sympathy that renders the mammæ dependant upon
the womb. It is well known, that they swell a little every month,
at the beginning of menstruation; that cancers are often formed in
them at the cessation of this natural discharge; that the voluptuous
sensation of coition sometimes extends even to them, &c. All physicians
have observed this sympathetic relation which appears to be of a
peculiar kind and to depend upon the analogy of the functions of the
sympathizing organs.

After severe acute diseases, especially idiopathic fevers, the
glandular action is oftentimes much increased; there are great
evacuations; these are the crises; it is, according to the opinions of
most, the morbific humour that is expelled. This is a phenomenon that
should be examined, and which certainly in many cases does not depend,
as I shall prove, on the cause to which it has been attributed.

Though I consider many of the secretory derangements in diseases as
sympathetic, I am far from thinking that all are so. Certainly in
many cases, there is a general affection of the whole system, an
affection in which the glands, like all the other parts, participate;
this is what takes place in idiopathic fevers. But when one system is
especially affected, as the cutaneous in the small pox, the measles,
scarlatina, &c. the serous in pleurisy, peritonitis, &c. the cellular
in phlegmon, the nervous in convulsions, &c. I call the derangement
which the others experience sympathetic, and which does not depend upon
an injury of their texture.

Other ideas may be attached to the word sympathies, but these are
what I have connected with it in diseases. The word is of but little
consequence, provided what it expresses is understood.


_Active Sympathies._

These sympathies are less frequent than the preceding. In the diseases
of the glandular system, we see however examples of them. The history
of inflammations of the kidneys, the salivary glands, the liver, &c.
shows us many phenomena arising sympathetically in the other systems
on account of the diseases of this. I do not speak of the derangement
of digestion and the circulation, functions which, naturally connected
with the secretions, are inevitably deranged when these are; I speak of
the organs, which having no direct relation with the diseased glands,
are yet affected, as we see in convulsions, spasms, wandering or fixed
pains in different places, sweats, &c.

The testicles in health exert a remarkable influence upon the organs
of the voice. We know that it becomes more harsh the moment they enter
into action, and that it changes when they are removed by castration;
this phenomenon is constant and invariable. Barthez believed that it
arose from the ordinary sympathetic phenomena; in fact, it appears
to be but a particular modification of that general influence which
the testicles exert on all the vital forces, which are uniformly
debilitated or strengthened, according as their action is feeble or
strong. Yet some organs are more disposed than others to feel these
affections. The pectoral mucous system is an example of this. Passive
hemorrhage of this system is frequently the consequence of excessive
excretion of semen; phthisis even is often the fatal effect of it.


_Characters of the Vital Properties. First Character. Life peculiar to
each Gland._

The glandular life, the result of the preceding forces considered in
exercise, is not uniform in the whole system, no doubt because its
texture differs in each gland, and because to each texture is given a
peculiar modification of vitality. Many phenomena result from these
differences which have been well observed by Bordeu.

1st. Each gland has certain substances with which it is exclusively in
relation in the natural state. Hence why the salivary glands do not
secrete bile, and the liver allows the materials of urine to pass in
its vessels without separating them; from this results the diversity
of secretions. Hence also why cantharides affect exclusively the
kidneys; why mercury acts especially upon the salivary glands; why
certain substances affect the testicles in a peculiar manner, increase
their secretion and even promote the excretion of the semen; why some
aliments give more milk than others. I am persuaded that certain
substances act upon the mucous glands and dispose them to a greater
secretion.

2d. Each gland has its peculiar mode of sympathies. We have seen that
the testicles sympathize especially with the pectoral organs, and the
liver with the brain. The kidneys, when affected with acute pain,
have an influence peculiarly on the stomach, and occasion vomiting.
The mammæ and the womb are directly and particularly connected in
sympathies.

3d. The inflammation of each gland has a particular character. That of
the kidneys does not resemble that of the liver, the testicles, &c. The
prostate gland when inflamed produces symptoms wholly different from
those of the testicles, &c. I do not speak of the differences resulting
from the diversity of the fluids, but only of those which arise from
the difference of texture.

4th. Each gland has its peculiar diseases, or such at least to which
it is disposed more than the others. Hydatids are very often found
near the convexity of the liver; they are never seen in the salivary
glands or the testicles. Though the parotid glands are as much exposed
to the action of external bodies as the testicles, there are twenty
sarcoceles to one scirrhus of these glands. The liver alone exhibits
that peculiar state that is called fatty; no gland is more frequently
the seat of steatomatous tumours. Physicians who have opened but few
bodies, employ the vague and insignificant word _obstruction_, &c. for
every kind of glandular swelling. But observe that most commonly these
swellings have nothing in common among them but the increase in size;
their nature is wholly different, and yet observe how ignorant many are
in medicine; they perceive by the touch that there is a hardness of the
liver, and immediately aperients, the acetate of potash, &c. are the
common means which they oppose to hydatids, to steatomatous tumours, to
scirrhi with granulations like marble, to fatty livers and to a hundred
different alterations from which the increase of size may arise, as
if it was this increase and not the kind of tumour that produced it,
which they had to combat. Give then also aperients when the liver
displaced by hydrothorax projects unnaturally, and you will act almost
as rationally.

5th. Each gland exhibits peculiar modifications in those evacuations
that are called critical, of which it is sometimes the seat after long
diseases, &c. &c.

6th. It is also to the difference of vitality of the different parts of
the glandular system, that must be referred the following phenomenon;
certain glands enter suddenly into action, either from a direct
irritation, or a sympathetic excitement, as the lachrymal for example,
which from a state of remission passes suddenly from the influence
of the passions, to that of copious secretion. On the contrary, it
requires some time to excite the other glands, as for example the
kidneys, pancreas, &c. which cannot suddenly pour out their fluids,
whatever may be the excitement they experience. The same stimulus
applied to the conjunctiva, produces a flow of tears, and at the same
time increases the action of the Meibomian glands; but the first effect
takes place before the other. The same stimuli applied to the mucous
surfaces can never produce a catarrhal discharge till the expiration of
some time.


_Second Character. Remission of the Glandular Life._

The second character of the glandular life, is that of being subject
to habitual alternations of increase and diminution. Sleep extends
especially to the animal functions; they alone are completely suspended
in the ordinary state, and it is this which constitutes sleep. But the
glands sleep also to a certain extent, though there is never a complete
suspension except in diseases. I would compare the sleep of animal life
to the intermissions of intermittent fevers in which the apyrexia is
complete, and the sleep of the glands to those of remitting fevers in
which the paroxysm is only moderated, though it always continues.

The saliva is copiously poured out when aliments enter the mouth, at
other times it only moistens this cavity. Whilst the chyme is passing
through the duodenum, the pancreas and liver moisten it abundantly;
they are also in action during hunger, but in an infinitely less
degree. I have convinced myself of this by many experiments upon the
comparative state of digestion and hunger; the substance of these
experiments I have given elsewhere. We know that it is some time after
eating before the kidneys commence their action. The intermissions of
the action of the mammæ are almost as real as those of the organs of
animal life. Each mucous gland has its time of secretion; it is that in
which the surfaces, to which the excretories go, are in contact with
any substance that is remaining there, or that is only passing.

The glands then must be considered as continually separating a fluid
from the blood, and as being at certain periods in greater activity,
and consequently as furnishing more fluids.

This remission of the glands appears to be owing to a cause nearly
analogous to that of sleep, which, in animal life, is produced by the
weariness the sensitive and locomotive organs experience, after long
continued action. The kind of weariness which the glands are capable of
experiencing, is not in general attended with a painful sensation, as
in animal life; its nature appears to be wholly different. Yet women,
after nursing too long, feel a pain in the breast that warns them to
leave off. The testicles become the seat of a painful sensation, when
the emission of semen has been many times forced.


_Third Character. The Glandular Life is never simultaneously raised in
the whole system._

The vital properties of the glands are never simultaneously excited
in all. When one is in action, the others are in remission. We might
say, that there is but a determinate quantity of life for all, and
that one cannot live more without the others living less. To this law
is the digestive order accommodated. In the first period the salivary
glands furnish at first a great quantity of fluid; in the second, the
parietes of the stomach; in the third, in which the chyme passes into
the small intestines, the liver and the pancreas are principally in
action; in the fourth, it is the mucous glands of the great intestines
which especially act; and finally the kidneys enter into a particular
action in order to evacuate the residue of the fluids. All the glands
cannot act at the same time; it is as in the external motions in which
certain muscles always rest whilst the others contract. The most
improper time for coition is that of digestion, because we then make
the mucous, hepatic, pancreatic secretions, &c. coincide with that of
the testicles. In diseases one gland increases its secretion only at
the expense of the others. Observation proves this every day.

We might, as I have said, make use of this remark, by producing in
various glandular and other affections, artificial catarrhs, a disease
which we can always produce on the mucous surfaces by the introduction
of a foreign body. I have for some time past made much use of ammonia
respired by the nose. Pinel prescribes it before the paroxysms of
epilepsy. There are an infinite number of other cases in which it is
very efficacious, as in some kinds of cephalalgia, in ataxic fevers,
in certain apoplexies, in various comatose affections, &c. A blister
does not act till the expiration of some time; it requires four, five,
six hours even for it to produce an irritation. Who does not know that
oftentimes in diseases in which the forces are much prostrated, it has
no action on the cutaneous system? On the contrary, the excitement of
the pituitary membrane by ammonia is always sudden on the one hand
and always efficacious on the other. Its effect, it is true, is only
instantaneous, but this is precisely its advantage; for in many cases
a blister is only useful the moment it irritates the skin; hence the
use of drying it immediately and reapplying it. The employment of
ammonia or of any other strong stimulant upon the pituitary membrane,
can be repeated every quarter of an hour, every five or six minutes
or even every minute. If habit renders the patient less sensible to
its excitement, we can replace it by another irritating substance,
whereas we cannot thus change the cutaneous excitement by a blister.
What I have said of the pituitary surface is applicable to those of the
rectum, the urethra and stomach, on which we can in many cases apply in
diseases excitements in a more advantageous manner than is done upon
the skin by means of blisters.

Moreover, the character of the glandular life of which we are treating,
is only an insulated modification of a character general to all the
vital properties, a character which consists in this, that they are
weakened in one place when they are raised in another. Hence why
the great collections of pus, large tumours and dropsies are always
attended with a weakness in the glandular action. It is upon this
character that rests the use of vesicatories, setons, moxa, cauteries,
&c. which do not act, as has been said, by evacuating the morbific
matter, but by making the irritation of the diseased part cease by that
which is produced elsewhere.


_Fourth Character. Influence of climate and season on Glandular Life._

Another phenomenon is also derived from the preceding character, and
it is one that may be likewise considered as characteristic of the
glandular system; viz. that in general it is in greater activity in
winter than summer, in cold climates than in warm. In fact, heat which
expands the cutaneous system increases the action of it at the expense
of that of the glands, and reciprocally cold which contracts it, by
preventing the constant exhalation that is going on there, forces the
glandular system to supply this action. Hence why the same fluid,
introduced into the economy, goes out with the urine in winter and with
the sweat in summer; why, if we wish to produce an immediate discharge
of urine in summer, it is necessary to suppress the perspiration by the
sudden application of cold to the surface of the skin, by descending
into a cellar, or some other subterraneous place; so that in summer we
can, after digestion, make the product of the fluids pass off with the
urine or the sweat, according to the temperature of the atmosphere in
which we digest; why teas and diuretics forbid the use of each other,
and why a physician who should employ them at the same time would know
but little of the laws of our economy; why most of the diseases that
are attended with an immoderate discharge of the secreted fluids, are
almost always characterized by a diminution of the exhaled fluids; why
in some seasons diseases have a greater tendency to be characterized
by sweats, and in others by urinary, mucous evacuations, &c. It is to
the greater degree of the vital activity of the glandular system in the
winter, that must then be referred the frequency of catarrhs, diseases
most of which suppose an unnatural increase of its action, the greater
facility with which the kidneys are influenced by cantharides, &c.
Physicians should have these considerations particularly in view in
their treatment. It is necessary to act more upon the glandular system
in winter, and the cutaneous in summer, because each system is as much
more disposed to answer to the excitements made upon it, as it actually
is in greater activity.


_Fifth Character. Influence of Sex upon Glandular Life._

Is the life of the glandular system more active in man than in woman?
As it respects the glands destined to digestion, the secretion of the
tears, the evacuation of urine, &c. there is but little difference
in the two sexes. As to genital glands, man has testicles and the
prostate; woman has mammæ, so that in this respect they seem to be
equal. Observe however that the influence of the first upon the
economy, is much greater than that of the second. It is from the womb
that go forth in woman the irradiations which correspond with those
which the testicles send to all the other organs.


ARTICLE FOURTH.

DEVELOPMENT OF THE GLANDULAR SYSTEM.


I. _State of this System in the Fœtus._

Though the secretions are not active in the fœtus, the glandular system
is in general much developed. All the salivary glands and the pancreas
are larger in proportion than afterwards; the liver is enormous; and
the kidneys have a size much greater in proportion than they have in
the adult. The same probably is true of the mucous glands, though I
have not made any very precise researches upon this point. The form is
different in many; the kidney for example is evidently uneven, whilst
afterwards its surface is almost smooth. The colour is not the same;
this is particularly striking in the salivary and lachrymal glands.
These glands which are white in the adult, have in the fœtus an extreme
redness which they lose by washing, which is not owing to the blood
circulating in their vessels, though there is much of it in their
vessels, but it is really inherent in their texture. This colour is
never as great in the pancreas, though its texture is nearly the same.
The texture of the glands is extremely soft and delicate at this age,
which is the case with all the parts. They are divided and yield with
great ease, and their vessels, which are large, carry into them a very
great quantity of fluid.

Then they are, if we may so say, in a state corresponding with that
of remission in the adult; they secrete even less fluid, though they
appear however to be in constant action. In fact, all the reservoirs
would be insufficient to contain their fluids, if in a given time, as
much flowed from them as after birth. Is this because the black blood,
which then enters their parenchyma, is unfit to furnish the materials
of the secretions? This may have an influence, and I have elsewhere
imagined it, from the circumstance that this blood is unable to support
many other functions. But the principal reason appears to me to be,
that in the fœtus the nutritive motion of composition predominates
evidently over that of decomposition, which is very inconsiderable.
Almost every thing which arrives in the organs remains in them and
continues to furnish the materials of the rapid growth which is then
taking place in the body; now, the secretions being principally
destined to carry off the residue of nutrition, must then be very
inactive.

Besides, digestion does not introduce into the blood any of those
principles which, being useless to nutrition, must on this account
go out as they entered, that is to say without making a part of our
organs; such are for example most of the drinks, which only pass into
the mass of blood, and go out immediately with the urine.

The glands of the fœtus are then like the brain at that age; though
much developed, they remain inactive; they are in the expectation of
action.


II. _State of the Glandular System during Growth._

At birth, the glandular system increases suddenly in energy; it takes
a life which until then was foreign to it, and begins to pour out more
fluid. It owes this change, 1st, to the difference of the blood which
enters it, and which till then black and consequently venous, then
becomes red and charged with principles that are new to it; 2d, to
the general and sudden excitement carried to the extremity of all the
excretories, by the aliments to those which open upon the canal that
extends from the mouth to the anus, by the air to the mucous ducts of
the bronchial and pituitary surfaces and to the lachrymal gland, by the
various frictions of the extremity of the glans penis and even by the
air which acts also upon it, to the kidneys and the bladder.

All the glands are so much the more sensible to this sudden excitement,
as they are unaccustomed to it. Their sensibility, heretofore torpid,
is roused; they feel the contact of the blood which enters them and
which till then had made only a feeble impression upon them. This
sensation is so much the more acute, as on the one hand the organic
sensibility of the glands becomes more evident, and as on the other
the red blood is a more powerful stimulus than the black; for, as I
have already had occasion to observe, the blood that arrives in an
organ produces two effects in it, one of which is to excite it, either
by the motion it communicates, or by the contact of the principles
it contains, and the other is to furnish materials for the different
functions, as for exhalation, secretion, nutrition, &c. The first
effect is common to all the organs which the blood enters; the second
is peculiar to each.

I would observe however that many of the secretions are much less
active during the first years, than they are afterwards; such are those
of the salivary glands, the liver, &c. The kidneys being destined to
throw out the residue of digestion, as much and more often than that
of nutrition, are in a state of activity in proportion to that of the
first function. The infant often passes urine, as he frequently voids
excrements. It is not because many substances, returning from the
organs which they have nourished, present themselves to the kidneys, to
be thrown out by this part.

The affections of the glandular system are not the predominant ones
in early age. 1st. It is not the parotids that are enlarged in the
frequent swellings that take place in their neighbourhood, but it is
almost always the lymphatic glands. 2d. We know that an excessive flow
of bile, and the affections which arise from it, are then very rare.
3d. All the secretions relating to generation are absolutely nothing.
4th. In the same proportion in which the organic affections of the
liver and the kidneys are common in the adult, are they rare in the
infant. Then it is in what are improperly called lymphatic glands,
in the brain, &c. that the morbid anatomist finds materials for his
researches; for observe that the organs which are particularly in
action in one age, are those which are most often attacked by acute
and chronic diseases at that age, and that on the contrary they seem
to forget those in which but little is done. 5th. Surgeons know that
sarcoceles, hydroceles by effusion, varicoceles and all the diseases of
the testicles are as rare before the period of puberty, when nutrition
only is going on in these glands, as they are common in the subsequent
years.

It appears that it is the mucous glands which are then the most
commonly affected and are consequently in the greatest activity. The
lachrymal glands are also very frequently in action. The infant weeps
more often than the adult; we might say that all the passions which
agitate this age have but one uniform mode of expression, and this
mode is weeping. If the infant suffers, if he is jealous or frightened
he weeps; if he is furious, he weeps because he is not very strong.
This influence of the passions upon the lachrymal gland in the early
years, seems to take place at the expense of the influence exerted
upon the other glands. It is rare that fear or fright give to infants
a sudden jaundice, or that they excite bilious secretions. At this age
they do not pass water and void their excrements from fright as often
as in the after ages; they have not the spasmodic vomitings that are
so frequently occasioned by the passions of the adult; they do not
become pale or red as much in anger; thus the countenance is not to
the same extent the moveable picture upon which is painted the emotions
of the mind. The eye does not sparkle in anger and is not expressive
in friendship. It is the lachrymal gland which then most often serves
in the face, for the expression of the passions. Observe that this
expression is that of weakness and want of power, it is that of woman,
who resembles the infant in so many phenomena. The feeble stag opposes
his tears to the dogs, who seize upon him to devour him.

The glandular texture remains for a long time soft and delicate in the
infant. At birth and in the fœtus, neither the liver nor the kidneys
have the singular property of hardening by boiling. They remain during
this experiment very tender and yield easily to the least impression.
If the boiling be ever so long continued, they do not lose this
character, which is gradually weakened as we advance in age, and which
at this period makes the glands fit for some uses in our kitchens to
which they are not so proper in the adult.


III. _State of the Glandular System after Growth._

Puberty commences about the period that growth finishes. A gland till
then inactive in man, enters suddenly into activity. The prostate
follows it in its development. In woman the breasts swell, separate,
and acquire in a short time a size which they would not have done
in many years, if they had grown according to the same laws as in
the preceding state. The other glands, far from being weakened, in
proportion as these become stronger, increase their action also; they
become stronger, and gradually lose the softness that characterized
them in infancy; they moreover grow harder.

Till then composition had predominated over decomposition in the
general nutritive motion. Then almost as many substances are constantly
thrown from each organ, as enter its interior to nourish it. Now as
the glands are the great emunctories which throw out the residue of
nutrition, they then pour out more fluids in proportion than before.

During youth it is the genital glands which predominate over the
others; they seem to be a centre whence go irradiations that animate
the whole machine. We might say most often that they are, in the
mechanism of our moral actions, the spring which puts every thing in
motion.

As we recede from youth, the influence of the genital glands becomes
weaker, because they are in less activity. Towards the thirty-sixth or
fortieth year, it is especially the glands destined to digestion which
predominate over the others, and among these the liver in particular
seems to be in activity. Then the bilious affections are predominant;
then the passions to which the bilious temperament seems to dispose
us, more frequently agitate the mind. Ambition, hatred and jealousy
are often the sad attendants of this age. These passions are then
more durable. The levity of youth and the passions arising from the
influence of the genital glands, which predominate at this age, had
for a time suppressed these, or rather had prevented them from being
developed. Then they remain alone, the others having escaped in smoke
with the fire of youth. Then also the influence of the lively emotions
of the mind affects especially the glands and the abdominal viscera.
Then is felt that contraction at the epigastric region, the painful
effect of the bad passions; jaundice occasioned by sorrow is then more
frequent.

This age is that of the organic affections of the glands, of all the
numerous changes of texture, of all the excrescences which destroying
as it were the nature of these organs, transform them into bodies of a
different texture. In infancy, leucophlegmasia is most often produced
by an engorgement of those lymphatic bunches that are called glands,
which resembles tabes mesenterica, the engorgement of the bronchial
glands, &c. In the adult on the contrary, it is with the diseases of
the liver, of the spleen, of the kidneys, that it is most often seen.


IV. _State of the Glandular System in Old Age._

In old age, the glands become more firm and hard. Before that period
even, the glandular system of animals ceases to be used at our tables.
The liver, the kidneys, the spleen, &c. are mixed with the fleshy
texture in common boiled meat, only to communicate to it some salts,
some savoury principles that are foreign to this texture. They are
not eaten, or at least they are not agreeable to the taste. The lungs
which contain so great a quantity of mucous glands, do not afford a
very digestible aliment except those of the calf; those of the ox are
not brought to our tables, especially when the animal is old. I would
observe upon this subject that the muscular and glandular systems are
in an inverse order as it respects digestion, at least in the stewed
state to which they are reduced for nourishment. In fact, the glandular
system has not an agreeable taste and is not very digestible except in
young animals, whilst at this age the muscular is insipid, and does not
become savoury food till towards the middle of life.

In extreme old age, the colour of the glands changes less than that of
most of the other organs. We find the liver, the kidneys, &c. almost
as full of blood as in the adult; they are as red, whilst the muscles
pale and colourless announce by their appearance that but little blood
enters them at the latter periods of life. We might say that this fluid
first abandons the skin and the muscles of animal life which in the
trunk are subjacent to it, and which in the extremities are found very
distant from the heart, or at least that it diminishes much in the two
systems, and is concentrated in the organs in the neighbourhood of
the heart; thus the secretions are still very abundant in old people,
whilst the muscular, nervous forces, &c. are considerably weakened. The
kidneys still secrete much urine; the liver pours out much bile, though
this gland loses in part the kind of predominance it exercised in the
economy towards the fortieth year. We know that the very frequent
catarrhs that then take place, indicate an increase of action in the
mucous glands. The functions of the testicles and mammæ have long since
ceased.

The activity of the glands remaining in exercise, appears to be owing
to two causes. 1st. The decomposition being very great at this age,
many substances are presented to the glands to be thrown out. An old
person decreases by a phenomenon opposite to the rapid growth of the
fœtus, in which the glandular system throws out scarcely any thing
from the economy. 2d. The skin having the horny hardness and being
contracted, ceasing in part to be an emunctory of the products of
decomposition, the glands supply the place of these functions. The
cutaneous and glandular systems are then in the same relation as in
winter and in cold countries, in which, we have seen, that the second
constantly supplies the place of the first.

In general, the glandular system is one of those in which life is the
most slowly extinguished. In the dead bodies of old people we find
the bile still filling the gall-bladder, the bladder full of urine,
&c. All the glands when compressed, the prostate itself, permit a
large quantity of fluid to escape from their excretories. I have even
observed that in this compression, we uniformly press out more fluid in
an old subject than in a young one. The older the animals are, the more
their kidneys, as we know, preserve the urinous smell. The lungs, which
abound so much in mucous surfaces and consequently in mucous glands,
are not withered and have not the horny hardening in old age; they
perform their functions as regularly as in youth.

In general it is a very remarkable phenomenon that all the principal
internal organs, the liver, the kidneys, the spleen, the heart, the
lungs, &c. still preserve a very considerable vital force, whilst the
sensitive and locomotive organs already almost exhausted, have broken
in part the communications which connect the individual with the
objects which surround him.




DERMOID SYSTEM.


All animals are covered with a more or less compact membrane, of a
thickness in general proportioned to the size of their body, destined
to defend the subjacent parts, to carry out a considerable portion of
the residue of nutrition and digestion, and to place it in relation
with external bodies. It is in man a sensitive boundary, placed at the
extremity of the domain of his mind, where these bodies continually
touch, for the purpose of establishing the relations of his animal
life, and of thus connecting his existence with that of every thing
which surrounds him. This covering is the _dermis_ or skin. We shall
call the whole of it the Dermoid System.


ARTICLE FIRST.

FORMS OF THE DERMOID SYSTEM.

The covering which forms this system, being proportioned to the parts
that it covers, is applied to these parts, adapted to their great
inequalities, and allows the largest external prominences to be
visible, but conceals a great number on account of their small size;
thus the appearance of the body stripped of skin differs very much from
that with the skin on.

This covering everywhere continuous is reflected through different
openings in the interior of the body and goes to give origin to the
mucous system. The limits between the two systems are always marked by
a reddish line; within this line is the mucous system, without it the
dermoid. Yet the demarcation is not as striking in the organization
as in the colour. Both are confounded in an insensible manner. In the
neighbourhood of these openings, of those of the face especially, the
dermoid becomes more delicate. At the commencement of these openings,
the mucous borrows more or less, as I have said, the characters of the
first.


I. _External Surface of the Dermoid System._

This surface, everywhere contiguous to the epidermis, is remarkable
for the hairs which cover it, for the oily fluid which constantly
lubricates it, for the sweat that is deposited on it, for the sense of
feeling of which it is the seat and which the internal surface does not
possess. We shall in this article consider only the external dermoid
forms, without regard to these different objects.

We see upon this surface different kinds of folds.

1st. Some are owing to the subjacent muscles which, being intimately
connected with the dermis, forming almost a part of it, wrinkle it
when they contract. Such are the wrinkles on the forehead; those in
the form of rays which the orbicularis produces around the eye-lids,
&c. those of which the cheeks are the seat, when the great and small
zygomatic, &c. contract; those which the orbicularis of the lips
produces around the mouth, when it contracts it by diminishing its
opening, &c. All these folds are owing to this, that on the one hand
the skin cannot contract like the muscles, and that on the other it
is necessary that it should occupy less space in length at the instant
these are shortened. They are of the same nature as those of which
the mucous surfaces, that of the stomach in particular, become the
seat in the contraction of the fleshy layer which is contiguous to
them. Thus the direction of these folds is always perpendicular to
that of the subjacent muscles whose fibres they cut at a right angle.
We are accustomed to attach much importance to the existence of these
wrinkles in the expression of the passions; no doubt because then they
are strongly marked. In fact the breadth of the face of man makes it
well adapted to their development, whilst that of animals is badly
formed to produce them. Thus their eye, rather than the features of the
face, is the moveable picture which is differently sketched at every
instant by the various feelings of anger, hatred, jealousy, &c. The
wrinkles of the human face contribute very much to the expression of
the countenance, they compose in part the physiognomy, and mark its
different shades.

The wrinkles of the scrotum are analogous to these; they depend upon
the contraction of the subjacent cellular texture, in which some fleshy
fibres appear also to exist.

2d. There are other wrinkles which are owing also to the motions, but
not to those of the subjacent muscles. There are those of the sole of
the foot, and especially those of the palm of the hand. There is not
there any sub-cutaneous muscle adhering to the skin, except the small
palmar muscle, which has no agency in these wrinkles that are formed at
the places where the skin is constantly folded in flexion. Thus there
are many of them about all the articulations of the phalanges. In the
palm of the hand, we see three principal ones, one at the base of the
thumb, produced by the motion of opposition, another at the anterior
part of the palm, occasioned by the flexion of the four last phalanges
which are bent towards the thumb, and the third is found in the middle
of the palm. The dermis is folded between these depressed lines, in
the motions in which the hand is hollowed. Many other small folds
corresponding with less evident and less frequent motions, cut these at
different angles.

On the back of the foot and hand, there are many wrinkles about each
articulation of the phalanges, when they are extended. They disappear
in flexion, and are owing to this, that nature, on account of the
motions, has made the skin more loose at this place, and broader in
proportion to the parts it covers. About most of the articulations,
there are analogous folds, but they are much less evident, because the
skin adheres less to the neighbouring parts. Upon the whole trunk, the
arm, the fore-arm, the thigh and the leg, we see no depressions but
those from the muscular prominences.

3d. There is a third species of wrinkles, or rather cutaneous
impressions, which are not very evident, found especially on the sole
of the foot and the palm of the hand and which we easily distinguish
from the preceding; they are those which indicate the rows of the
papillæ. The surface of the trunk presents hardly any thing similar.

4th. Finally, there are the wrinkles of old age, which are of a wholly
different nature. The sub-cutaneous fat having in part disappeared, the
skin becomes too large for the parts it covers; now as it has lost with
age its contractility of texture, it does not contract, but folds in
various directions. Thus where there was the most fat, as on the face,
these wrinkles are the most evident, they resemble those that appear on
the abdomen after several pregnancies, dropsy, &c. In young people, if
emaciation takes place suddenly, the skin contracts, and no wrinkle is
formed.


II. _Internal Surface of the Dermoid System._

This surface answers everywhere to the cellular texture which is loose
upon the trunk, the thighs, the arms, &c. and which is condensed
upon the cranium, the hand, &c. In most animals, a fleshy layer
called panniculus, and of a form analogous to that which is almost
everywhere subjacent to the mucous system of man, separates the skin
from the other parts, and communicates to it various motions. In man,
the dermoid system exhibits here and there traces of this internal
muscle, as is observed in the platysma myoides, the occipito-frontalis
and most of the muscles of the face. There is nothing similar on the
trunk, extremities, &c. Man is as much inferior in this respect to most
animals, as he is superior by the arrangement of his facial muscles.
Thus observe that whilst in him all the passions are painted as it
were upon the face, and the whole exterior of the trunk remains calm
in these tempests of the mind, this exterior is convulsively agitated
in animals. The mane of the lion becomes erect, the whole skin of the
horse moves, a thousand different agitations animate the exterior of
the trunk of animals, and make it a general picture on which is painted
all that passes in the interior. You can determine from behind, in
many animals, by seeing only their bodies, that they are agitated with
passion; cover the face of man, the curtain is drawn over the mirror of
his mind; thus almost all nations leave it uncovered. The physiognomy
is in this respect, if we may so say, more generally spread over the
exterior, in animals with a fleshy panniculus.

Besides the cellular texture, the dermis is almost everywhere
subjacent to the muscles in the trunk; but, foreign to the motions of
these muscles, it receives no sensible influence from them. In the
extremities it is found separated from the fleshy layers by aponeurotic
expansions. Many vessels wind under it; the great veins pass through
its texture; many arterial ramifications go upon its surface, and many
nerves between these ramifications.


ARTICLE SECOND.

ORGANIZATION OF THE DERMOID SYSTEM.


I. _Texture peculiar to this Organization._

This texture comprehends, 1st, the chorion; 2d, that which is called
the reticular body; 3d, the papillæ. The chorion is the essential part
of the dermis; it is that which determines its thickness and form. The
reticular body appears to be but little distinct from it. The papillæ
arise from it also, but are more evident.


_Chorion._

The chorion is of a very variable thickness. 1st. In the head, that
of the cranium and that of the face exhibit an opposite arrangement.
The first is very thick and also dense and compact, which is owing
especially to the numerous hairs that go through it. The second,
everywhere fine and delicate, is particularly so upon the eyelids and
the lips. 2d. The chorion of the trunk is posteriorly and all along the
back, of a thickness almost double that of its anterior part, where it
is nearly the same upon the neck, the chest and the abdomen. I would
except however that of the penis, the scrotum, the great labia and the
mammæ, in which its delicacy is greater than any where else. 3d. In the
superior extremities it is nearly uniform upon the shoulders, the arm
and the fore-arm; on the hand it increases a little in thickness and
more in the palm than on the back. 4th. This thickness is generally
much more evident on the thigh and the leg, where there are more
muscles, than on the arm or the fore-arm. On the foot, it increases as
on the hand, less in the dorsal than in the plantar region, which is
the thickest of all the parts of the dermoid system; which is owing
principally in the natural state to the arrangement of its epidermis.
We see from this, that though everywhere continuous, the chorion is
very different in its different parts. The relation of its thickness
with its functions is easily perceived on the hand, the foot, the
cranium, &c. Elsewhere we cannot so well see the reason of these
differences, which are notwithstanding as constant.

Woman has a chorion generally less thick than that of man; compared in
all the regions, it exhibits in the two sexes a sensible difference; on
the mammæ especially, it is much more delicate in woman. That of the
great labia however is proportionally thicker than that of the scrotum.

In order to understand perfectly the intimate structure of the chorion,
it is necessary to examine it at first on its internal surface, after
having carefully separated it from the fatty cellular texture, to which
this surface adheres more or less intimately. We see then that it is
differently arranged according to the regions.

1st. On the sole of the foot and the palm of the hand, we observe an
infinite number of white fibres, shining like aponeurotic fibres,
which are detached from this internal surface, form upon it a kind of
new layer, cross each other in all directions, leave between them,
especially towards the heel many spaces of different sizes, that are
filled with fat, separate more and more, and are finally lost in the
sub-cutaneous texture, nearly as the fibres of the brachial aponeurosis
insensibly disappear in the neighbouring cellular texture. Hence why
when we dissect the palmar and plantar integuments, we experience the
greatest difficulty in separating them entirely from the cellular
texture which is interlaced with these fibres; hence why also these
surfaces have not, on the parts which they cover, the mobility which
many others exhibit.

The density of the cellular texture contributes also something to this
arrangement which is essential to the functions of the foot and the
hand, which are designed to seize and grasp external bodies.

2d. The dermis of the superior and inferior extremities of the
back, of the neck, of the thorax, of the abdomen, of the face even
and consequently of almost all the body, is distinguished from the
preceding, because the fibres are much less distinct, and are not
lost in the cellular texture by being as it were confounded with it,
whence arises a remarkable laxity of the skin of these parts, and the
very great facility with which it is dissected; in a word because the
spaces between these fibres are much more narrow. These spaces appear
like an infinite number of holes irregularly placed at the side of each
other, containing most of them small fatty parcels of the neighbouring
texture, and exhibiting, when these small parcels have been carefully
removed, very evident vacuities. The fibres which form them, are
sufficiently near each other, to make you believe at first view, that
it is a surface pierced with an infinite number of holes, that has
been applied under the skin. On the contrary, on the hand and the
foot, towards the heel especially, it is a true net-work the spaces of
which are larger than the fibres that form them; this is the reverse
here. Be that as it may, these spaces in the internal surface of the
chorion are very favourable to the action of tannin which penetrates
the texture infinitely better from this side than from the opposite,
because it insinuates itself into these numerous openings. I have had
occasion to observe it in the human chorion which I have had tanned
for the purpose. Chaptal has observed that the epidermis is a real
obstacle to the action of tannin, and that on this account scraping
is a preliminary operation essential to tanning, since it allows the
skin to be penetrated on both sides; but even when thus scraped, it
receives the tannin much more easily on the side of the flesh than on
the opposite one.

3d. The chorion of the back of the hand and the foot, as well as
that of the forehead does not exhibit these numerous openings on its
internal surface; it is smooth and white, especially when it has been
macerated a little. It is precisely the same as that of the scrotum,
the prepuce and even the great labia. The texture of it is more
compact, no space is left in it, so that though more delicate than that
of the extremities and the trunk, it contains almost as much substance.
As to the chorion corresponding to the hair and the beard, we see in it
only the openings necessary for the passage of the hairs, and which are
wholly different from those of which I spoke just now, which form real
culs-de-sac, and do not pierce through the chorion.

Hence the internal face of the dermoid chorion exhibits three very
distinct modifications. The first and last are seen to a small extent,
whilst the second is almost general, with some differences however in
the trunk, the extremities and the head. Besides, these modifications
do not suppose a diversity of nature, but only of forms. Much separated
and arranged in fibres in the first, the dermoid texture is compact and
condensed a little in the second, and by this condensation renders the
spaces less distinct. But there is a means of seeing them everywhere
very well, where there is the least trace of them, and this is by
maceration. This means also shows the dermoid texture best. In fact,
when the skin has remained for some time in water, it softens, the
fibres of its chorion separate, and their interstices become more
distinct; then we see that the spaces exist not only on the internal
surface, but that they extend into its texture which appears to be
truly like a sieve in its whole thickness, so numerous are the spaces
arising from the interlacing of the fibres.

These spaces do not terminate in culs-de-sac towards the external
surface; they open upon this surface by many foramina which are very
evident in a skin that has been macerated for a month or two, and
which, in the ordinary state are almost imperceptible in some subjects,
and very visible in others. Besides, in order to see them it is
necessary to remove the epidermis; now as with the view of producing
this effect immediately we commonly employ the action of boiling
water or fire, the dermoid texture by this means acquires the horny
hardening, and they become much less apparent, whereas maceration not
only does not produce horny hardening of the skin, but it expands and
dilates it, which renders these foramina very evident. In some parts of
the skin and in certain subjects, we might then introduce the head of
a pin into them; in others they are less evident. These foramina never
pierce the dermis perpendicularly, all open obliquely to its surface;
so that a perpendicular pressure tends to close them and bring their
parietes in contact. I cannot compare their termination better than
to that of the ureters in the bladder; hence why the hairs which go
through them are never perpendicular, but oblique to the skin. We speak
incorrectly when we say that the hairs are planted obliquely; their
insertion in the bulb is perpendicular; it is in their passage through
the chorion that they change direction.

Besides, these foramina are not vessels, but mere communications
from the interior to the exterior through which pass the hairs, the
exhalants, the absorbents, the blood-vessels and the nerves which
go to the surface of the dermis; thus the subjacent spaces are only
cells in which are contained the vessels of the glands and of the
cellular texture. The dermoid texture should then be considered as a
real net-work, as a kind of cellular texture, the cells of which very
evident within, become less so on the exterior surface, with which all
communicate to transmit to it different organs. The chorion is then
the outline, the frame, if I may so say, of the cutaneous organ. It
serves to lodge in its spaces, all the other parts which enter into the
structure of this organ, and contributes to give them the form they are
to have, but is wholly foreign to them.

What is the nature of this texture, which enters especially into the
composition of the cutaneous chorion? I know not; but I think it has
much analogy with the texture of the fibrous system; the following
considerations support this analogy. 1st. On the heel, where the
dermoid texture has the fibrous form of the irregular ligaments, it
would be almost impossible to distinguish it from it, so uniform is
the external appearance; it has the same resistance and density; the
same sensation is experienced when it is cut with the bistoury. 2d.
The dermoid texture becomes yellow and transparent like the fibrous
by stewing. 3d. It melts gradually like it into gelatine. 4th. Like
it, except the tendons however, it strongly resists maceration. 5th.
Sometimes these two textures are identified; for example, the annular
ligaments of the wrist evidently send elongations to the neighbouring
dermoid texture. 6th. This texture can serve, like the fibrous, for the
insertion of muscles; we see it in the face, where many of the fibres
of the orbicularis of the lips and the eyelids, and almost all those of
the eyebrows, find real tendons in the fibres of the dermoid texture.
There is the same arrangement in the cutaneous palmar muscles.

All these considerations evidently establish many relations between the
dermoid and fibrous textures. Yet they are far from being the same. To
be convinced of this it is sufficient to observe how much their mode
of sensibility differs, and how different also are their diseases; it
seems at first as if there was no analogy between them in this double
relation. Yet the line of demarcation is by no means as great as it
appears to be. In fact the acute sensibility of the skin is not seated
precisely in this white texture, which is interwoven so as to leave
between its meshes the spaces of which we have spoken, and which we
see especially on the surface adhering to this organ. The experiment
mentioned in the article on the mucous system, and in which I irritated
the cutaneous organ from within outwards, evidently proves it. It is
the surface on which the papillæ are found that especially exhibits
this vital property.

On the other hand morbid anatomy proves that the internal surface
of the dermis, in which are especially found the texture and the
spaces of which we have spoken, is entirely free from most cutaneous
eruptions. This is no doubt true as it respects the small pox, the
itch and many species of herpes; I have satisfied myself of it as to
the vaccine vesicles, the miliary eruption, &c. &c. It is certain that
in erysipelas, the external surface only of the chorion is coloured
by the blood which enters the exhalants; thus the slightest pressure,
causing the blood to flow back, produces a sudden whiteness which soon
disappears by the return of the blood into the exhalants. It is this
which forms the essential difference between simple erysipelas and
phlegmon, in which not only the external face of the chorion, but its
whole texture and the subjacent cellular one are inflamed. In measles
and scarlatina, the redness is also very evidently superficial. These
phenomena accord with those of injections; for if they succeed at all
in children, the skin of the face and less frequently that of the other
parts, becomes almost entirely black. Now this blackness is much more
evident on the external than the internal surface of the skin, no doubt
because more exhalants are found in the first than in the second, which
the arterial trunks only traverse.

The preceding considerations evidently prove that the texture of the
internal surface of the chorion, and even that of its interior, have a
vital activity much less than that of the external surface; that this
texture is disconnected with all the great phenomena which take place
upon the skin, with those especially which relate to the sensations and
the circulation; that it is in the papillæ that the first are seated
and in the reticular body the second; and that it is almost passive
in nearly all the periods of activity of this double portion of the
dermis. Its functions, like those of the fibrous texture, suppose it
to be almost always in this passive state; they are only to defend the
body and to protect it from the action of external bodies. It is this
which forms our real covering; thus its properties are well adapted
to this use. Its resistance is extreme. It requires very considerable
weight to tear very narrow strips of chorion, when it is suspended from
them; drawn in various directions, these strips are broken also with
much difficulty.

Yet this resistance is much less than when tannin is combined with
the chorion. We know that when thus prepared, this portion of the
skin affords the strongest strings we have in the arts. I know but
two textures in the animal economy, which unite to such an extent
suppleness and resistance; these are this and the fibrous texture; and
this is a new character which approximates them. We have seen that
it requires a very considerable weight to break a tendon, a strip
of aponeurosis, or a ligament taken from a dead body. The muscular,
nervous, arterial, venous, cellular textures, &c. yield infinitely
more easily. If the dermoid texture had less extensibility, it might
advantageously supply the place of the tendons, the ligaments, &c. in
the structure of the body.

Since the chorion is foreign to almost all the sensitive and morbid
phenomena of the skin, let us inquire then in what part of the dermis
these phenomena are seated. These parts exist very evidently on the
external surface; now we find on this surface, 1st, what is called the
reticular body; 2d, the papillæ.


_Of the Reticular Body._

Most authors have considered the reticular body as a kind of layer
applied to the external face of the skin between the chorion and the
epidermis, pierced with an infinite number of openings through which
the papillæ pass. I do not know how we can demonstrate this layer,
which escapes according to the opinion of most of them, when the
epidermis is detached. In order to see it I have employed a great
many means, but no one has succeeded. 1st. Such is the adhesion
of the epidermis to the skin, that in a sound state we can hardly
separate them without injuring one or the other. Yet with the greatest
precaution we see nothing mucous on the chorion when it is laid bare.
2d. A portion of skin cut longitudinally, especially from the foot
where the epidermis is very thick, allows us to see very distinctly on
the divided edge the boundaries of this and of the chorion; now nothing
escapes from about the line which separates them. 3d. In ebullition in
which the epidermis has been removed, nothing remains upon the internal
surface, nor upon the chorion. 4th. Maceration and putrefaction, the
latter especially, produce upon the chorion a kind of glutinous layer
the instant the epidermis is removed. But this layer is entirely the
product of decomposition. Nothing similar is met with in the ordinary
state.

I believe, from all these considerations, that there is not a substance
deposited by the vessels upon the surface of the chorion, extravasated,
stagnant upon this surface, and representing there a layer in the sense
in which Malpighi understood it. I believe that we ought to understand
by the reticular body, a net-work of extremely fine vessels, whose
trunks already very delicate, after having passed through the numerous
pores with which the chorion is perforated, come and ramify upon its
surface, and contain different kinds of fluids.

The existence of this vascular net-work is placed beyond a doubt
by fine injections which change the colour of the skin entirely
externally, without altering it much within. This is, as I have
observed, the principal seat of the numerous eruptions most of which
are really foreign to the cutaneous chorion.

We may then consider the reticular body as a general capillary system,
surrounding the cutaneous organ, and forming with the papillæ a layer
between the chorion and the epidermis. This system contains in most
men, only white fluids. In negroes, these fluids are black. They have
an intermediate tinge in the tawny nations. We know how much the shades
vary in the human race. Hence the colouring of the skin resembles
nearly that of the hairs, which evidently depends upon the substance
existing in their capillary tubes; it is analogous to that of the
marks at birth, that are commonly called nævi materni, and in which we
never see a layer of fluids extravasated between the epidermis and the
chorion.

Moreover, I think we know but little as yet concerning this substance,
which fills a part of the external capillary system. It does not
circulate in it, but appears to remain there till another replaces it.
When we examine the skin of a negro, we see a black teint, and that is
all. In maceration I have observed that this teint is sometimes removed
with the epidermis, and that it sometimes remains adhering to the
chorion. It is very evidently foreign to both, since both have the same
colour in whites as in blacks. It is never reproduced, after it has
been removed; for cicatrices are white in all people.

Is there in white people a white substance which, remaining in the
external capillary system, corresponds to that of negroes, or does the
colour of their skin depend only upon the epidermis and chorion? I
have been tempted to believe that they also have a colouring substance,
since the long-continued action of a powerful sun evidently blackens
them. This circumstance has even made me believe that whiteness is
natural to all men, and that there was but one primitive race which has
degenerated according to different climates.

But in order to be convinced of the diversity of races, it is
sufficient to observe, 1st, that the teint of the skin is but one of
the characters which distinguish each race, and that many others are
always united to it. The nature and form of the hair, the thickness
of the lips and the nose, the width of the forehead, the degree of
inclination of the facial angle, the whole appearance of the face, &c.
are constant attributes which indicate a general modification in the
organization, and not merely a difference of the dermoid system. 2d.
White people become tawny in hot countries; but they never acquire the
teint of the people of the country. 3d. Removed to cold countries in
early age, or even born in them, the blacks always remain so; their
shade hardly changes at all from generation to generation. 4th. Colour
by no means follows temperature exactly; we see many varieties in the
shades of people who live under the same degree of latitude, &c.

Every thing proves then that the colour of the skin is but an insulated
attribute of the different human races, though it is that which is most
striking to our senses, and that we should not attach to it a greater
importance than to many others which are drawn from the stature, which
is oftentimes very small, as in the Laplanders, from the broad and
flat face, as in the Chinese, from the dimensions of the chest, of the
pelvis, the extremities, &c. It is from the differences of the whole,
and not from those of an insulated part, that the lines of demarcation
should be made which separate the races. The European face and forms
are in general the type with which we compare the exterior of the
other nations. The ugliness or beauty of the human races are, in our
way of considering it, measured by the distance which separates these
races from ours. Such is in fact the force of habit with us, that we
rarely judge in an absolute manner, and that every object which is much
removed from those to which we are accustomed, is disagreeable to us
and sometimes even disgusting.

Besides, the colouring matter of the cutaneous reticular body is more
interesting to the naturalist than to the physician. What should
particularly arrest the attention of the latter is the portion of the
capillary system exterior to the skin in which the fluids circulate.
In fact, besides the portion which is the seat of colour, there
is evidently another that the white fluids constantly pervade, in
which they are moved with more or less rapidity, and in which they
continually succeed each other. It is from this portion that the
exhalant pores arise which furnish the sweat; it is this vascular
net-work which is the seat of erysipelas and of all the cutaneous
eruptions that are foreign to the chorion.

The blood does not penetrate it in an ordinary state, but a thousand
causes can at every instant fill it with this fluid. Rub the skin
briskly, and it reddens in a moment. If an irritant is applied to
it, whether it acts mechanically like nettles, the appendices of
which penetrate the epidermis, or exerts a chemical action, like the
frictions with ammonia, or the action of fire when a portion of skin is
held too near it, instantly the sensibility of this vascular net-work
is raised; it invites into it the blood which it formerly repelled;
every part of a surface reddens in proportion to the irritation. If
passion acts powerfully upon the cheeks, immediately a sudden redness
is evident in them. All rubefacients exhibit moreover a proof of the
great tendency which the sensibility of the superficial capillary
system of the dermis has to place itself, if it be ever so little
excited, in relation with the blood which in the ordinary state is
foreign to it.

Vesicatories depend upon the same principle. Their first effect is to
fill with blood the cutaneous capillary system, where they are applied,
to produce in it a sudden erysipelas, and then to occasion a copious
serous exhalation under the raised epidermis. They effect in a few
hours what most cases of erysipelas do in many days; for we know that
most of them terminate by vesicles which are raised above the skin.
In burning, carried sufficiently far to be more than a rubefacient,
and yet not so as to produce the horny hardening, there is also a
sudden increase of exhalation under the raised epidermis. In general
the production of every cutaneous bladder is always preceded by an
inflammation of the external surface of the skin. This phenomenon is
not exclusively confined to this system. We have seen the serous, as
soon as it is laid bare and irritated considerably, redden in a short
time by the passage of the blood into its exhalants; which constitutes
an inflammation to which often succeeds a copious exhalation of milky
or other kind of serum. This exhalation does not remain upon the
surface, and does not form vesicles there, because it has no epidermis;
this is the only difference between these phenomena, which at first
view do not appear to be the same in the serous and cutaneous systems.

It is not only the irritation of the cutaneous organ which makes the
blood pass into the external capillary system. Whenever the heart is
powerfully excited and it accelerates the course of this fluid, it
always tends to go into it; this is what is evidently seen, 1st, after
violent running; 2d, in the hot period of a paroxysm of fever.

Upon this subject I will make a remark which appears to me to be very
important; it is that the capillary system of the face is, more than
that of all the other parts of the skin, exposed to be thus penetrated
with blood. 1st. This is evident in the two cases of which I have just
spoken, and in which the action of the heart is increased. 2d. In the
passions, the skin remains the same in the other parts, whilst that
of the face suddenly becomes pale or red. 3d. We know that physicians
frequently examine the state of the facial capillary system, which is
almost always affected by the state of the internal viscera, and is
full of blood or empty, according as it is sympathetically influenced.
4th. In various kinds of asphyxia, in those especially produced by
submersion, by the vapour of charcoal, by strangulation, &c. the face
is uniformly of a violet colour from the passage of the black blood
into its external capillary system, into which it is brought by the
arteries. Oftentimes the neck and the upper part of the chest are also
livid; but there is never a discoloration of the inferior parts. 5th.
In many diseases, in which death takes place by a kind of asphyxia,
because the lungs are the first interrupted, the dead bodies have a
violet-coloured and swollen face; this may be easily observed by all
who frequent dissecting rooms. There are a hundred subjects in which
the head has this lividity, to one in which it is observed in the
inferior parts. 6th. Most cases of apoplexy produce the same lividity
of the face.

To what is this extreme susceptibility of the facial capillary
system to admit the blood owing? Three things, I think, principally
contribute to it. 1st. The course is already opened to this fluid,
since the redness of the cheeks necessarily supposes its presence in
them, it only increases in quantity; whereas when another part of the
dermoid surface becomes red, all the blood which enters it is almost
accidental. 2d. The anatomical arrangement of the capillary system is
more favourable to this passage there than elsewhere; for it appears
that the communications of this system with the arteries of the chorion
are more free. What proves this is, that in injections the face is
coloured with great ease. There is undoubtedly no anatomist who has
not been struck with this phenomenon, especially in children, in whom
if the coarse injections of our dissecting rooms succeed at all, the
face becomes wholly black, whilst the fluid penetrates but very little
into the other parts of the cutaneous system. 3d. It appears that
there is a greater sensibility in the face; in fact the same irritant
brings blood there, which does not make it flow to any other place. For
example, a blow equal to a box on the ear does not redden the skin of
the arm, whilst it suddenly inflames the cheeks.

The blood disappears from the facial capillary system as it enters
it; in an instant the passions will successively produce there the
bright red of a paroxysm of fever, the whiteness of syncope and all the
intermediate shades. It is even the extreme ease with which this fluid
penetrates this system, that renders the face well adapted to serve as
a kind of picture, which the passions paint by turns with a thousand
shades, that are effaced, altered, modified and return again according
to the state of the mind.

I would observe upon this subject that the passions have in the face
three means of expression; 1st, the capillary system, a means wholly
involuntary, and which often betrays what we wish to conceal; 2d, the
muscular motion, which, by contracting or expanding the features,
expresses the melancholy or gay emotions, and to which belongs as
effects, the various wrinkles of which we have spoken; 3d, the state
of the eye, an organ, which, as Buffon has remarked, not only receives
the sensations, but also expresses the passions. The two last means are
to a certain extent voluntary; we can at least disguise them; whereas
we cannot deceive by the first. The actor imitates anger, joy, &c.
because we can give these passions by contracting the eye-brows, by
dilating the face in laughing, &c. But it is the rouge of the actress
that imitates modest chastity; it is by removing this rouge that she
imitates the paleness of fear, horror, &c.

I will add another essential observation in respect to the facial
capillary system; it is that it appears that its tendency to receive
blood, disposes it to become the more frequent seat of many affections.
We know, 1st, that erysipelas is much more frequent in this than in
other parts; 2d, that the variolous pustules are remarkably conspicuous
here; 3d, that many eruptions are more abundant here than elsewhere.

From all that we have just said, it is evident that it is necessary
to distinguish two portions in the capillary system exterior to the
chorion. 1st. One is constantly filled with the colouring substance of
the skin, a substance which appears to be stagnant like that of the
hair of the head, and that of the hair of the body, which is subjected
only to the slow and insensible motion of composition and decomposition
and which never exhibits that sudden increase or diminution of which we
have just spoken. 2d. The second is constantly pervaded by many fluids
which continually succeed each other there, and which constantly escape
by transpiration, and which are replaced by the blood, that insinuates
itself into this portion of the capillary system. These two portions
are entirely independent, and have probably no kind of communication.

It appears that at the instant of death there remains a certain
quantity of the white fluids in the second portion of the exterior
capillary system; the following experiment, which I have frequently
made, proves it; by plunging a portion of skin into boiling water, and
leaving it there an instant, the epidermis is raised up, not as a whole
as in a blister, but in an infinite number of small vesicles which are
formed suddenly on its surface, and which contain a serous fluid, that
escapes as soon as we open these vesicles.


_Papillæ._

We call by this name those small eminences that arise from the external
surface of the chorion, and which, piercing the capillary net-work
of which we have just spoken, become by their extremities contiguous
to the epidermis. These eminences are very evident in the palm of the
hand and the sole of the foot, where they are regularly arranged, in
the form of small curved striæ in different directions. We see them
through the epidermis, notwithstanding its thickness in these places.
But they are seen especially when this has been in any way removed,
as by maceration, ebullition, &c. If we cut longitudinally a portion
of the chorion of the foot, with its epidermis adhering to it, we see
between them along the divided edge, a line in the form of a curved
thread, which arises from these small eminences placed at the side of
each other.

In some other parts of the skin, we distinguish the papillæ in a very
evident manner; but in a great number, the epidermis being removed,
we see only a surface, slightly uneven from some small eminences,
especially towards the orifices through which the hairs and the vessels
pass, but we do not discover those regularly arranged eminences, the
papillæ properly so called.

We must not mistake for them the numerous and very evident prominences,
which render the skin of some subjects extremely rough. These
prominences are formed by small cellular, vascular or nervous bunches,
by sebaceous glands, &c. which are found near the small openings by
which the chorion opens under the epidermis, and usually transmits the
hairs. These bunches, lodged in the small oblique canals which are
terminated by these openings, raise the external side of them and thus
form this prominence. The following very curious experiment proves
this arrangement; when the skin is macerated for two or three months,
or even less, on the one hand these little bunches in which there
is almost always a little fat, are changed into that white, thick,
unctuous matter, analogous to spermaceti, into which fat kept a long
time in water is always converted; and on the other, the foramina
enlarging, as we have seen, and the skin changing into a kind of pulp,
we can easily remove it all around these little prominences, and see
that they are continued with the fat which fills the meshes of the
subjacent chorion, and which is also changed into a hard matter.

Injections have evidently proved to me that there were vessels in
these cellular bunches, and I have been convinced of it for some time
past by the dissection of some subjects that died of scurvy, in whom
the spots commenced by very small ecchymoses, similar as it were to
flea-bites, and which occupied these little eminences. The petechiæ
of adynamic fevers have a different appearance; but they belong also
to an extravasation of blood in the cellular texture, occupying the
small pores which open on the exterior of the chorion to transmit the
vessels, the hairs, &c. The more prominent these eminences are, of
which we have spoken, the more uneven is the skin. In general they are
more frequent on the extremities and on the back, than on the anterior
part of the trunk. In the extremities there are more of them in the
direction of extension, than in that of flexion.

We attach the idea of a beautiful skin, to that in which these small
tubercles are not found, and in which the chorion is united at its
external surface. Women have commonly this last arrangement more
evident than men. The epidermis which covers these eminences very
often scales off at that place, especially from strong friction, which
contributes still more to render the skin uneven, rough and harsh to
the touch where they exist, which might induce a belief that they are
formed by it, though it is always only accessory to them. Where it
is very thick, as in the palm of the hand and the sole of the foot,
it cannot be raised, and these small cutaneous tubercles are never
seen. In the face where many vessels pass from within outwards, by the
little pores of which we have spoken, we meet with hardly any more of
them. The papillæ scattered among these eminences, are in general very
slightly apparent in the places where they exist.

All anatomists attribute to these last a nervous structure; they regard
them as the termination of all the nerves that go to the skin, and
which, according to them, are expanded to form these, after having
first left their external covering. Some even say that they have traced
filaments even into the papillæ; I confess that I have never been able
to do it. In the ordinary state, the density of the chorion and the
extreme delicacy of the filaments, are evidently an obstacle to it. In
the state of long continued maceration, in which the chorion becomes
pulpy and in which we might consequently trace these filaments, were
it ever possible, it cannot be done. I do not however deny the texture
attributed to the papillæ. The acute sensibility of the skin seems even
to suppose it; but it is only analogy and not demonstration, which
establishes this anatomical fact; indeed all the other senses, whose
organs are so sensible, have the portion of them which receives the
impression of bodies continuous with a nerve.


_Action of different bodies upon the Dermoid Texture._

In most of the other textures, we have only considered this action in
the dead body, because during life, these textures always removed from
external bodies, cannot be influenced by them. Here we can regard it in
a double relation, since the skin is incessantly in contact with almost
all the bodies of nature.


_Action of Light._

Light evidently acts upon the dermis. Removed from its influence, men
are blanched, if we may so say, like plants. Compare the inhabitant
of a city, who is never exposed to the influence of the sun, with
the peasant who constantly is, and you will see the difference. It
appears that it is the light and not the heat which produces the effect
of which I have already spoken; for individuals who live in a warm
temperature, but removed from the solar light, become white like those
of cold countries. Thus we know that some men who keep their chambers
always very hot, are whiter than others who, living in a less hot
atmosphere, are constantly exposed to the sun. We might remain forever
in a bath of a temperature equal to the warmest seasons, and the skin
would not blacken. Apartments for study which are warmed with stoves,
and in which men remain as long as the labourer at his plough, are as
warm as the atmosphere of summer, and yet the skin of those who occupy
them never becomes darker. Besides an irresistible proof is that the
clothing which does not prevent the action of caloric upon the skin,
and which offers a barrier to the rays of light only, prevents the
cutaneous colouring that takes place upon the parts which the light
immediately strikes, as upon the hands, the face, &c.

I do not speak of the solar influence upon the vital forces of the
skin, as in cases in which sun-strokes produce erysipelas, or as when
light is employed medicinally to recall the life of a part; but it is
only in relation to the dermoid texture that I consider its action.


_Action of Caloric._

The action of caloric upon the skin exhibits very different phenomena,
according to the degree of it that it is applied.

1st. A warm atmosphere expands the dermoid texture, increases its
action, and makes most of the fluids which form the residue of
nutrition and digestion, pass off by the exhalants.

2d. When contracted by cold, this texture refuses to admit those
fluids, which then go off principally by the urine.

3d. The insensible change from one to the other of these two states,
does not disturb the functions. When this change is sudden, there are
almost always alterations in different organs, because the fluids
destined to pass out, cannot vary their direction as rapidly towards
this or that organ, as the cutaneous excitement produced by the sudden
changes from heat to cold.

4th. The skin resists a temperature much greater than that of the body;
it opposes an insurmountable barrier to the external caloric, which
tends to an equilibrium in animate as well as inanimate bodies. Thus
whilst these last are penetrated with this fluid in a medium warmer
than themselves, and soon acquire the temperature of this medium,
living bodies remain at the same degree, how much greater soever the
surrounding heat may be to their own. The curious experiments of
the English physicians have placed this truth, as it respects man,
beyond a doubt. It is unnecessary to give the detail of these well
known experiments, in which the mercury was seen to descend in the
thermometer, when the bulb was placed in the mouth and in which the
skin became covered, in a heated room, with the aqueous vapours of the
air, which the greater cold of the body condensed upon its surface. A
slight attention to animals with cold blood, living in warm climates,
proves the same thing. I will make one remarkable observation upon this
point, it is, that most reptiles, whose temperature is much less than
that of the mammalia and of birds, and who consequently are brought
much nearer than them to the temperature of winter, cannot however
support it. They become torpid and sleep in subterraneous places, the
heat of which remains nearly uniform like that of cellars, and do not
awake till the milder temperature of spring stimulates them.

5th. The skin, in very cold climates, seems to be on the other hand an
obstacle which prevents the internal caloric from suddenly escaping and
thus placing the body in equilibrium with the surrounding medium. This
is evident in countries near the pole. Upon this subject an observation
the reverse of the preceding can be made; it is that the cetaceous
animals inhabit seas the temperature of which is most unlike their
own. Whales are sought for especially in the latitudes of Greenland,
Spitzbergen, &c. Why do fishes with warm blood delight in the frozen
seas, whilst the amphibious animals with cold blood prefer the burning
heat of the sun? I know not.

Let us observe that most of the internal organs when exposed in
solutions of continuity, have not the faculty of preserving as well as
the skin, a degree of independent temperature. They become cold or hot
sooner than it as long as they remain healthy. The intestine brought
out of the abdomen in the operation for hernia, a muscle laid bare, &c.
&c. exhibit this phenomenon; thus in order to give them this faculty of
having an independent temperature, nature inflames them, and they thus
constantly preserve their heat, whatever may be that of the surrounding
medium. The mucous surfaces next to the skin resist the surrounding
temperature the most, as is seen in prolapsus of the rectum, in
inversion of the anus, &c. This difference among the different systems
is probably owing to that of their structure.

6th. When the action of caloric is carried to a very considerable
extent, it begins to act upon the skin, and its effects are the more
evident in proportion as it is the more intense. 1st. The slightest of
these effects is to produce an evident redness, a kind of erysipelas;
the caloric then acts like a simple rubefacient. 2d. The second is to
redden the skin and then to produce vesicles on it. 3d. In the third
there is a real horny hardening, a crisping of the fibres of the
chorion which contract, like those of all the animal textures exposed
to too strong a degree of heat. 4th. In the fourth and last effect,
the dermoid texture is burnt, blackened and reduced to mere carbon.
These different degrees of burning arise only from different degrees of
caloric. I would observe that in the two first effects, this fluid acts
upon the vital forces, and that these two effects cannot consequently
take place except during life. The two last are exerted only upon the
texture of the organ; thus they take place after death precisely as
before. Cooks often employ the horny hardness, to give to the skin a
hardness and brittleness necessary in some kinds of cooking.

7th. Cold carried to a great degree acts also upon the cutaneous organ,
and produces different effects, according to its intensity. The first
of these effects is very analogous to the first effect of a slight
degree of caloric. It consists of a kind of local inflammation. The
tip of the nose, the ears and the fingers, the cheeks, &c. become red
from a slight degree of cold. I have not accurately observed the other
effects between this and the last, which consists in a sudden privation
of life. But there is this difference between the gangrene that then
takes place, and that produced by a high degree of caloric, that the
blackness is sudden in this last, whereas it takes place only as a
consequence in the other. Observe in fact that there is in gangrene
two things which physicians do not sufficiently distinguish, 1st, the
mortification of the part; 2d, its putrefaction. The mortification
is always antecedent; it is produced by a thousand different causes;
sometimes by the ligature of an artery, as in aneurism; sometimes
by that of a nerve; often by violent inflammation; sometimes by a
contusion, attrition, a bruise, &c. Whenever a part is dead in the
midst of those which live, whatever may be the cause of its death, it
becomes putrid precisely like a dead body, every part of which life has
left. Putrefaction takes place then even sooner, because on the one
hand the natural heat of the body, and on the other the moisture of
the surrounding parts, favour it remarkably. This putrefaction varies
according to the state in which the part was at the instant of death.
If much blood infiltrated it, as when inflammation destroys life, it
quickly becomes putrid, blackens immediately and allows a fetid sanies
to escape; this putrefaction is called moist. If there is but little
blood in the part at the instant of death, its putrefaction is less
sudden; it first putrifies, then blackens, and allows but little sanies
to escape; this is the dry gangrene. Thus in a dead body, if one part
is much loaded with blood, as the head of those that have died of
apoplexy, its putrefaction is much more rapid and moist than that of
the parts in which this fluid is less abundant. In the gangrene which
succeeds mortification produced by cold, there is often dryness of the
part, because there was but little blood in it at death. How little
many physicians know of the progress of nature in the employment of
antiseptics, which they apply in the living economy, as upon flesh
without life. Antiseptics are applied for one of two purposes, either
to prevent the death of the part, or its putrefaction. 1st. If it is
with the first intention, antiseptics should be varied. By untying the
artery of a limb of an animal that has been tied, you will perform
an antiseptic operation. Bleeding and emollient applications which
lessen the violence of inflammation in a phlegmon, are antiseptics.
A tonic as wine and all stimulants which excite the vital forces in
a part in which they are languid after a bruise, are antiseptics.
This word is then extremely improper when it is applied to medicines
designed to prevent the mortification of the parts. Antiseptics are
employed to prevent a dead part in the midst of living ones becoming
putrid; some effect is obtained; thus by sprinkling cinchona, muriate
of soda, or any neutral salt, by moistening a limb, a portion of skin,
the extremity of the nose, &c. which is dead from any cause, the
putrefaction will be arrested, as in a dead body upon which the same
means are employed. But what will be the result of it? a little less
fetor in the surrounding parts and less danger of their receiving
the influence of the emanations of the dead part; but it is always
necessary that this should come off; antiseptics will never bring it
to life. Hence it is evident that these means should be considered in
two points of view entirely different. The first prevent mortification,
and vary remarkably though they are designed to effect the same
object; thus our means of curing retention of urine are very variable,
oftentimes opposite, according to the cause which tends to produce this
retention. The others prevent putrefaction, without restoring the parts
to life; now these are uniformly the same, whatever may have been the
cause of the local death.


_Action of the Air._

The air acts incessantly upon the cutaneous organ. In the ordinary
state, it constantly removes from its surface the sweat that is exhaled
from it. Fourcroy, who has paid particular attention to the solution
of the transpired fluid by the surrounding air, appears to me to have
allowed too much influence to this solution upon transpiration. In
fact there are two very distinct things in this function; 1st, the
action of the exhalants which throw out the fluid; 2d, the action of
the air which dissolves and evaporates it. Now the first of these is
wholly independent of the other. Whether the fluid is dissolved or not,
more is still furnished by the exhalants. If the solution does not
take place, the fluid accumulates upon the skin, which remains moist;
but this moisture does not obstruct the exhalant pores and prevent
new moisture from being added to it. A comparison will render this
very evident. In the natural state, the serous fluids are constantly
exhaled and absorbed; the absorbents perform for them the functions
of the air which dissolves the sweat; now, though these vessels cease
to act, as in dropsies, the exhalants continue their action; there
arises only a serous collection, which, though applied to the orifices
of the exhalants, does not prevent them from pouring out more serum.
The bladder in vain contains urine which presses upon the opening of
the ureters, these ducts do not pour less into it. Though the mucous
juices become stagnant on their respective surfaces, new juices are
however poured upon these surfaces. So though the skin remains moist
from the want of solution of the transpiration, more transpiration is
nevertheless exhaled. Solution is a physical phenomenon wholly foreign
to the vital phenomenon of exhalation. We transpire in a bath as well
as in the air; only the fluid which arises from it is mixed with the
water, instead of being reduced to vapour.

The moisture of the skin is owing to two causes wholly foreign to each
other; 1st, to the increase of the fluid furnished by the cutaneous
exhalants; now the action of these exhalants may be increased from
three causes. First, every thing which accelerates the motion of the
heart, as running, the paroxysm of acute fevers, &c. drives to the
skin, as it is commonly expressed. In the second place, every thing
which tends to relax and expand the cutaneous organ by a direct action
exerted upon it by the surrounding bodies, increases also the action of
these exhalants, as in the great heat of summer, as in a bath and after
coming out, as in a heated room, &c. In the third place, the action
of the skin is in many cases, sympathetically increased. Here may be
classed the sweats of phthisis of which the lungs are the source; those
of fear, which depend upon a sudden affection of an epigastric organ;
those of many acute diseases, &c. Now in all these cases, however
active the solution by the air may be, the skin will be constantly
moist, because there is thrown out upon it more fluid than the air can
dissolve. Thus in catarrhs of the lungs, in which more mucous juices
are thrown into the bronchia than the air can remove, it is absolutely
necessary that there should be cough and expectoration to carry off the
remainder.

2d. There are cases in which the moisture of the skin arises from the
solution not being sufficient. This is what takes place in the moisture
of the bed in which the air is not changed, in damp weather, &c.
There is not then more fluid exhaled; but the ordinary fluid becomes
evident, because it is not dissolved. It is under this point of view
that we must consider the action of the air upon the cutaneous organ
which transpires. It carries off nothing in this organ; it has no real
action upon it; it takes only what its vessels throw off. Solution
is merely accessory, it is always subsequent to exhalation, and has
no relation with it. In the same day, in which the temperature has
remained the same, the skin is often dry, moist, humid and even wet
with sweat. If the air acts upon transpiration, it is by contracting
or relaxing the exhalants, and not by dissolving what they throw out.
If the skin formed a sac without an opening, like the serous surfaces,
transpiration would go on though it was removed from the contact of the
air, the same as if in contact with it. Why in fact should not that
take place there, which does upon these surfaces?

If we consider the action of the air upon the skin of the dead body,
we see that it produces two different effects, according to the state
of the body. If the air penetrates the skin on all sides, it dries it,
and it then acquires a sort of transparency, like the fibrous organs,
unless a large quantity of blood had been accumulated in it at the
moment of death, in which case it becomes black or of a deep brown.
Thus dried, 1st, it is firm and resisting, but can be bent in various
directions without breaking, as is the case with many textures thus
dried, as the cartilaginous, the muscular, &c. &c. 2d. It is much less
easily altered than most of the other textures in a dried state. 3d. It
absorbs moisture less easily than them, though however when immersed
for a long time in water, it finally resumes nearly its original colour
and loses its transparency. 4th. It does not exhale a very disagreeable
odour, like many of the other textures. Hence why the skins of animals,
merely dried, are used in many of the arts; why some barbarous people
make use of them for clothing, &c. The aponeuroses, and the mucous,
serous and fibrous membranes could not be thus employed. It is to this
also that must be attributed the little alteration that takes place in
the exterior of mummies, which would never last for ages, if clothed
with a fleshy or serous covering.

When the skin is left upon the dead body, or exposed to a moist air, it
becomes putrid instead of drying. Then it takes at first a dull colour,
then a green and finally a black one. It exhales a very great fetor,
swells and thickens, because the gases which are disengaged there fill
the cellular texture in its little spaces. A mucous covering is spread
upon its external surface, which is deprived of its epidermis. Nothing
similar to this covering is seen on the internal surface. Finally,
when all the fluids it contains are evaporated, there remains a black
residuum, very different from that which is left after combustion.


_Action of Water._

This action during life, is relative either to the substances that
are deposited on the surface of the skin, or to the cutaneous texture
itself.

The sweat deposits incessantly upon the epidermis many substances, the
principal of which are taken away by the air, but many being slightly
soluble in it, as the salts for example, remain on its surface, and
adhere to it when not removed by friction. Mixed with the unctuous
fluid which oozes out upon this surface, and with the different
foreign particles that the air deposits there as everywhere else,
these substances form upon the skin a deposit which cannot, like the
transpiration, be carried off by solution. Now water removes all this
deposit; hence why the use of baths is truly natural. All quadrupeds
bathe themselves. All birds frequently plunge into the water; I do
not speak of those for whom this fluid is as it were the element. It
is a law imposed upon all species of animals whose skin throws out a
considerable quantity of fluid. All the human races hitherto observed
frequently plunge into brooks, rivers, or lakes, along which they
take up their abode. The countries that are well watered are those
which animals prefer. They avoid those where this fluid is wanting, or
in which it is only sufficient for their drink. We oppose nature in
every thing in society. In our own, numerous classes hardly ever use
a bath; thus you must seek especially in these classes for cutaneous
diseases. We have seen that the mucous juices, remaining too long upon
their surfaces, irritate and stimulate them and cause there various
affections. Is it astonishing that the residuum of the cutaneous
exhalation which the air does not remove, should occasion various
alterations upon the skin? In summer, baths are more necessary, because
as many excretions are taking place by the skin, more substances are
deposited there. In winter, in which every thing passes off by the
urine, the cutaneous surface becomes less dirty, and has less need
of being cleansed. After severe diseases, in which there has been
copious cutaneous evacuations, one or two baths terminate the treatment
advantageously. Let us consider water then as acting as accessory to
the air upon the skin, as removing from its surface substances which
the first cannot dissolve, substances, which varying remarkably like
those that compose the urine, have presented the transpiratory fluids
to chemists, sometimes as alkaline, sometimes as acid, oftentimes as
containing salts, sometimes charged with odoriferous substances, &c.
Water is the general vehicle; when it is evaporated, it leaves the
substances that are not volatilized like it. It is on this account that
dry frictions are also advantageous; they clean the exterior of the
body.

As to the action of the bath upon the cutaneous texture, we know but
little of it during life. They say in medicine that it softens, relaxes
and unbends this texture; this is vague language to which no precise
meaning is attached, and which is no doubt borrowed from the relaxation
which the skin of dead bodies undergoes, or even tanned leather, when
exposed to water. A bath acts upon the vital forces of the skin, raises
or diminishes them, as I shall say; but it leaves its texture in the
same state; it is only that of the epidermis which it alters, as we
shall see.

Macerated in water of a moderate degree of temperature, in that of
cellars for example which does not vary, the human skin softens, swells
but little, becomes evidently whiter, and remains for a long time
without experiencing any other alteration than that of a putrefaction
infinitely less than that of the muscular, glandular, mucous textures,
&c. subjected to the same experiment. This putrefaction, which removes
the epidermis, appears to be much greater on the side nearest to this
membrane; at the end of two or three months the skin loses but little
of its consistence. It does not become pulpy as the tendons and muscles
in this length of time when macerated; it does not become a fetid pulp
till the end of three or four months. I have preserved some of it for
eight months, which has still its primitive form, but which feels
liquid under the fingers when pressed a little. In the half putrid
state, the skin still preserves the faculty of crisping from the action
of caloric; it moves about when placed on burning coals, or when
plunged into boiling water. When once reduced to a really putrid state
it loses this property.

Exposed to ebullition, the dermoid texture when well separated from
the cellular, furnishes less scum than the muscular, the glandular and
the mucous; it resembles in this respect the tendons, no doubt because
being almost wholly gelatinous, it contains but little albumen. In the
horny hardening that takes place a little before ebullition commences,
it twists and then always becomes convex on the side of the epidermis,
and concave on the opposite side; and for this reason; the fibres of
the chorion in contracting by the horny hardening, are pressed against
each other; all the spaces which exist between them are effaced; now,
as these spaces are very large in the second direction, the dermoid
texture necessarily becomes more contracted there, whilst in the first,
the spaces hardly existing at all, every thing being almost solid,
the fibres have less space to contract, they remain longer, and the
surface continues larger. In the natural state the cavity of these
spaces, being filled with cellular texture, increases the extent of the
internal surface; this space then disappearing, this surface becomes
contracted.

The moment this kind of twisting takes place upon the skin, it is
covered, as I have said, with an infinite number of vesicles filled
with serum, and which are formed by the epidermis. As this membrane
is very thick on the soles of the feet, and the palms of the hands,
it cannot contribute in those places to their formation, and we see
nothing there similar to them. Yet by removing it from feet that have
been boiled, I have observed that it contained between its layers
many small vesicles, which were scarcely visible. I have not analyzed
the water of these vesicles, but presume it is analogous to that of
blisters. Besides a greater or less quantity of it is poured out, and
the vesicles are consequently larger or smaller, according to the
state of the external capillary system at the instant of death.

By the horny hardening, the skin becomes hard, elastic, very resisting,
thicker, but not so broad. It soon loses its semi-transparency and
yellowish colour, like the boiled fibrous organs. Then the hardness
it had acquired at the instant of the horny hardening is gradually
lost; it softens, gives out much gelatine in the water in which it
is boiled, does not lessen in size, but even increases in thickness.
Every kind of fibre, vacant space and organization is then gone; it
is a membranous mass, homogeneous in appearance, semi-transparent and
gelatinous. In this soft state, it does not lose the elasticity it had
acquired in the horny hardening, like the mucous, serous, cellular
textures, &c. &c. The great quantity of gelatine it contains still
preserves this property in it. The least motion that is communicated to
it produces a general trembling, a sort of vibration of all its parts,
exactly analogous to that of the various kinds of animal jellies, half
coagulated, which vacillate in the vessel from the least jar.

Finally, the ebullition still continuing, the gelatine is almost all
dissolved, and there remains only a residuum like membrane and which
disappears with great difficulty; it requires even a very long time
for common boiling water to reduce the skin to this residuum. Such are
the phenomena of the ebullition of the human skin as I have carefully
observed them. Chemists have paid great attention to the dermoid
texture of many other animals; they have formed different ideas of its
nature; they have admitted that there are two substances in it; one
fibrous and the other gelatinous. I refer to their works upon this
point, particularly to the labours of Seguin, and the work of Fourcroy;
for in general I do not relate what is detailed by others, it would be
only a useless repetition.


_Action of the Acids, the Alkalies and other Substances._

The sulphuric, nitric and muriatic acids act upon the skin, when in
contact with it, as upon all the other animal substances. I have
remarked however that their action is much slower, especially on the
side of the epidermis, though this membrane may have been previously
taken off. The first of these acids reduces it easily to a blackish
pulp; the others bring it to a pulpy state with more difficulty, even
when they are very little weakened; the oxy-muriatic acid produces
hardly any effect upon it.

Some authors have said that the lapis infernalis produces the same
phenomena on the dead as on the living body. I wrapped up in a piece
of skin, as in a rag, many fragments of this substance, so that they
were in contact with the epidermis; at the end of a day they were
reduced to a kind of pap of a yellowish red, by the moisture which they
had absorbed. The dermoid texture, crisped and contracted, had not
been penetrated; it did not appear even to have been injured on the
exterior. In general the action of the alkalies appears to be wholly
different during life, and it varies even according to the different
degrees of vitality. We know that flaccid and fungous flesh burns
much less easily than that which is red and vigorous. It is the same
with the acids. Never during life do they produce any thing analogous
to that pulp of different colours according to the acids that are
employed, which is always after death the result of their action.

We know that an alkaline solution, put in contact with the skin,
produces a kind of unctuous and slippery feel, which is no doubt owing
to the combination of the alkali with the oily deposit of the skin,
from which arises a sort of soap.

I shall not speak of the tendency of the dermis to combine with tannin,
nor of the phenomena of this combination; I should only be able to
repeat what others have said upon this point. I will merely remark
that it would be very important to try the effects of tannin on the
large sub-cutaneous aponeuroses, the texture of which being essentially
gelatinous has much analogy with that of the dermis, and which from
their extent and delicacy might serve for uses to which the dermoid
texture when tanned is less adapted. We know that the tanned skin is no
longer what it was in the natural state, and that the substance with
which it is then penetrated gives it an artificial consistence. If much
tannin has been combined with it, it loses entirely the faculty of
acquiring the horny hardness, and becomes brittle; whilst if but little
of this substance is added to it, it preserves in part its suppleness
and the property of crisping from the action of caloric. I would
compare tanned skin to bone penetrated with the phosphate of lime, and
that which is not tanned, to the cartilaginous parenchyma from which
the acids have removed this phosphate.


II. _Parts common to the Organization of the Dermoid System. Cellular
Texture._

The whole dermis is penetrated with a large quantity of this texture.
It is arranged in the following way; from the exterior of the
sub-cutaneous cellular layer, an infinite number of elongations is
detached which penetrate the contiguous spaces of the chorion, enter
afterwards into those which are more exterior, and finally terminate
in the numerous pores which transmit outwards the vessels, the nerves
and the hairs, which have previously passed through this cellular
texture. We can then consider the chorion as a kind of sponge, the
spaces of which represent the interstices, and which the cellular
texture penetrates on all sides; so that if it was possible to separate
by dissection, these spaces from the cellular texture, and the
organs which are in it, there would be a kind of sieve pierced in all
directions. Art cannot arrive at it but with difficulty on account of
the delicacy of the parts; but that which is not done by dissection,
nature often effects. In biles I have observed that all that which
fills the interstices of the dermoid fibres disappears by suppuration,
and that these fibres, separated besides by the swelling of the parts,
exhibit truly the appearance of a sieve of which I have just spoken,
when the fluid that moistens them is removed. The bile differs in
fact from many other cutaneous eruptions, in this that it attacks the
cellular texture of the spaces of the chorion, whilst they have their
seat, as I have said, in the reticular body. I do not know any acute
affection which attacks the chorion itself; all have their seat either
on its surface, or in the cellular texture of its cells. Its dense
and compact texture seems, like that of the aponeuroses, not able to
be changed until a length of time. In elephantiasis I have seen this
texture evidently disorganized.

M. Thillaye showed me portions of skin taken from a cemetery, in which
every thing that filled the dermoid spaces had disappeared, and in
which these spaces and their dried fibres formed a real membranous
sponge through which the light could everywhere be seen. In this case
the reverse of what is seen in long continued macerations had taken
place, in which the fatty cellular texture, changed into a solid, white
substance, preserves, as I have said, the form of the spaces which
it filled, whilst the dermoid fibres reduced to the pulpy state, are
easily removed. In the first case it is the mould only which is left;
in the second it is the substance which is contained in it.

In chronic leucophlegmasia, the sub-cutaneous serum gradually extends
along the cellular elongations of the spaces of the dermis, separates
their fibres, consequently enlarges these spaces, and sometimes
penetrates even to the epidermis, which it breaks in different places,
and through the crevices of which it escapes. In this case, there is
not resolution of the skin into cellular texture, as it is called, but
a separation of the dermoid fibres, which always remain.

I do not presume that the cellular texture of the chorion extends to
its external surface, under the epidermis; for when this has been
removed, fleshy granulations are not formed, now, in all the parts
where the cellular texture is found, these granulations are produced,
when the parts are laid bare.


_Blood Vessels._

The arteries winding in the sub-cutaneous cellular texture, furnish
an infinite number of small branches which are introduced with the
cellular parcels into the most internal dermoid spaces, afterwards pass
into those that are nearer, approximate by winding and anastomosing
a thousand times through the spaces of the external surface of the
chorion, finally go through the pores of this surface, and give rise to
that external capillary net-work of which we have spoken in the article
upon the reticular body, and to which in the ordinary state but very
little red blood comes. In this course through the dermoid spaces, but
few small arteries remain in the fibres of the chorion itself, as fine
injections prove. These fibres resemble in this respect those of the
aponeuroses through which many vessels pass, but which have but few
belonging to their own texture.

The veins follow nearly the motion of the arteries, but in an inverse
direction. After having passed through the dermoid spaces and the
cellular texture which fills them, they go to the great sub-cutaneous
trunks, which run a long course, form, as we have seen, a system wholly
distinct by its position from that of the arteries and which can be
often traced through the integuments. Not seen in the natural state,
the venous ramifications of the spaces of the chorion are considerably
dilated in the subjacent cancerous tumours, and make the skin which
covers these tumours appear to be marked with blue lines, which always
grow larger as the tumour increases. Whenever there is a considerable
distention of the cutaneous organ by an aneurism, pregnancy, dropsy,
&c. this dilatation also takes place, provided the cause of the
distention pursues a chronic course; for nothing similar is seen in
acute affections, whatever swellings may have taken place, as in those
consequent upon fractures, upon compound luxations, &c.

All the black blood formed in the skin goes into the general venous
system; no portion belongs to the abdominal.


_Nerves._

Their distribution is nearly the same as that of the blood vessels.
Many very considerable branches, as different divisions of the
musculo-cutaneous, the internal cutaneous, the lumbar, the saphena,
the anterior tibial, the intercostals, the cervicals, &c. form a kind
of sub-cutaneous nervous system, from which go all the branches that
enter the dermis. These branches, in passing through the dermoid spaces
with the arteries and the veins, appear to anastomose often together,
go through the pores which terminate the spaces on the interior, and no
doubt form the papillæ. Observe even that on the hand where the papillæ
are very evident, there are, in proportion to the surface, many more
sub-cutaneous nerves than any where else.


_Absorbents._

Many absorbents creep under the skin; it is here that they can be
the most easily studied. All the veins are surrounded with them;
various fasciculi are observed in their interstices; so that a layer
of absorbents, arranged in the form of a continuous layer, seems to
separate, in the extremities, the aponeurosis and the skin. There is
no doubt that the origin of the most of these vessels exists in the
chorion, that they carry to the blood the fat and the cellular lymph
of its spaces, and the nutritive matter of its fibres. But is there a
particular order of branches opening upon the surface of the epidermis
to absorb in certain cases foreign substances? This question cannot be
answered by anatomical inspection. But the following considerations
appear to me to throw great light upon it.

1st. The sub-cutaneous absorbents, visible by injections, are too
numerous in proportion for the mere purpose of carrying back the fat
and serum of the neighbouring parts.

2d. There are many medicines which appear to be evidently absorbed;
such are mercury in the venereal disease, various purgative and
emetic substances, febrifuges even, as cinchona, which, when applied
by friction, have produced their effects as well as if taken by the
stomach; cantharides often act upon the kidneys, when the tincture is
used as a liniment, narcotic substances sometimes occasion a weight in
the head and drowsiness when they have been externally applied, &c.
These different effects are well known and many authors have given
examples of them.

3d. There is we know absorption of different kinds of virus, of that
of hydrophobia, of the small-pox, of the venom of the viper, &c. an
absorption, it is true, which rarely takes place when the epidermis
is whole, but which uniformly does, when this being removed, the
matter is found in contact with the external capillary net-work of
which we have spoken. I would remark even that the different kinds of
inoculation of the small-pox, of the vaccine disease, &c. evidently
prove both the existence and importance of this net-work, to which
heretofore sufficient attention has not been paid. There are many
contagious principles which are absorbed through the epidermis; such
are those of the plague which the clothes communicate and those of
different pestilential fevers which penetrate by the skin more than by
respiration. I believe cutaneous absorptions from which diseases arise
may be divided in the following way:

                                       {1st, local, as the itch, herpes,
  1st. Absorptions which take place    {  tinea capitis, &c. &c.
    through the epidermis, and which   {2d, general, as pestilential
    produce an effect                  {  diseases, putrid fevers taken
                                       {  in an unhealthy place, &c. &c.

                                       {1st, local, as the vaccine
  2d. Absorptions which take place     {  disease, the small-pox, &c. &c.
    only when the epidermis is removed,{2d, general, as hydrophobia, the
    and from which arises              {  venom of the viper, a wound
    an effect                          {  with an instrument impregnated
                                       {  with putrid matter, &c. &c.

We see by this table that the absorbents when charged with injurious
substances, sometimes do not transmit them beyond the part and
sometimes carry them to the blood, which conveys them to the different
organs of the economy. Some authors have thought that in those cases
in which the effects of the absorption become general, there is rather
nervous action and sympathetic phenomena, than the transmission of
an injurious matter into the circulation, and that consequently the
solids take almost an exclusive part in these diseases. But to remove
all doubt upon this point it is sufficient to observe, 1st, that, in
the absorption of many contagious substances, for example, when from
the puncture of the finger with a scalpel impregnated with putrid
substances, a pain is produced, there is even a redness along the whole
course of the absorbents of the arm, and the axillary glands afterwards
swell; 2d, that by transfusing into the veins most of the substances
that are applied in frictions, effects analogous to those which take
place in these frictions are produced. Thus purgatives and emetics,
transfused or absorbed, act upon the intestines and stomach the same
as if introduced in any other way. It seems to me that sufficient use
has not been made of the experiments of the last age upon transfusions.
By comparing their effect with that which takes place upon the
cutaneous organ, I think that it is impossible not to admit a morbific
principle in the blood, at the time of contagious diseases.

3d. After the use of mercury taken in frictions, the emanations of this
metal from the animal fluids, act evidently upon silver when placed in
the mouth, the rectum, &c. I am persuaded even that the blood which
in the natural state exerts but very little action upon this metal,
would alter it then. Accoucheurs know that the waters of the amnios of
those women who have made use of mercurial frictions exhibit the same
phenomenon.

4th. Many substances that are not medicinal can be transmitted to the
blood by cutaneous absorption. Water appears to enter it in this way,
in the rapid production of certain dropsies, in those cases related of
travellers, who wanting fresh water on the ocean, have in part quenched
their thirst by surrounding themselves with damp clothes, &c. When our
garments are impregnated with the oil of turpentine, the urine soon
acquires an odour that is owing to the principles transmitted to the
blood by absorption. Many judicious philosophers have asserted that the
weight of the body has been increased by a walk in the morning.

I have observed that after remaining in the dissecting room some time,
the intestinal flatus frequently acquires an odour exactly similar to
that which the bodies in putrefaction exhale. In the following way
I convinced myself that it was the skin as much as the lungs that
absorbed these odorous particles. I closed my nostrils, and fitted
a long tunnel to my mouth, which passing out of the window allowed
me to breathe the external air. The flatus from my bowels, after I
had remained an hour in a small dissecting room, at the side of two
very fetid bodies, acquired an odour nearly similar to theirs. I have
observed also that by touching for a long time fetid substances, the
flatus acquires more of this odour, than by remaining only in an air
loaded with cadaverous exhalations. Then the absorbents carry at first
these exhalations to the blood, which afterwards throws them out by the
mucous surface of the intestines. Thus when the urine is absorbed, the
saliva, the mucous juices, &c. have an urinous odour.

I could accumulate many other proofs of cutaneous absorption; but I
have selected only the principal. Many others have been cited; Haller
in particular, to whom I refer, has multiplied examples of it.

I would remark however that cutaneous absorptions have a character
of remarkable irregularity; that under the same apparent influence,
they sometimes take place and sometimes do not. It is thus that most
often we absorb nothing in a bath, that we escape or take contagions,
that the vaccine disease is or is not communicated, that the variolous
inoculation is also often uncertain, &c. This is not astonishing. It
requires a certain degree of sensibility in the skin for the absorption
of this or that substance; above or below this degree, the absorbents
repel this substance. Thus in the intestinal canal, if you raise by a
purgative, the ordinary degree of sensibility of the lacteals, they
cease immediately for a time to take up drinks, chyle, &c. and every
thing passes off by the anus. Now a thousand causes act incessantly
upon the skin; a thousand irritants by turns applied to it make the
degree of its organic sensibility vary every instant, increase,
diminish and remove it from that which is necessary for absorption.
Is it astonishing then that this function should exhibit so many
varieties? Many modern philosophers have produced numerous negative
facts against cutaneous absorption. What do these facts prove? only
the varieties of sensibility which I have noticed; but they do not
destroy the mass of positive facts, generally acknowledged and which
together form a body of proof which nothing can oppose. Thus we have
seen the mucous surfaces variable in their vital forces on account
of the variety of their excitants, vary also in their absorption.
If in the serous membranes, in the cellular texture, in the work of
nutrition for the organs, this function is uniform, it is because being
constantly in contact with the same bodies, the surfaces where it is
going on have an uniform degree of organic sensibility.

Many facts, in relation especially to contagions seem to prove that a
state of weakness is favourable to cutaneous absorption. 1st. Children
and women absorb more easily than strong and vigorous men. 2d. Many
physicians have observed that in the night in which the cutaneous organ
is in a state of remission in this respect, as it is not stimulated
by external objects, contagious diseases are more easily taken. 3d. I
have remarked that most of the pupils who have fallen sick during my
dissections, had carried to their chambers portions of subjects, the
emanations from which had been able to affect them during sleep. 4th.
We know that practitioners recommend, that persons should not expose
themselves to contagious miasmata during hunger, as the forces are then
languid on account of the emptiness of the stomach.


_Exhalants._

The external capillary system which surrounds the chorion and embraces
the papillæ, appears to be the origin of these vessels, as it is the
termination of the arteries of the dermoid spaces. The exhalants take
up their fluid there, which they throw out upon the epidermis. We have
no anatomical knowledge as to their form, their length, their course
and their direction; but their existence is incontestibly proved, 1st,
by injections, which are sometimes poured out upon the whole cutaneous
surface; 2d, by the sanguineous exhalation which takes place in some
diseases in which there is a real bloody sweat; 3d, by the natural
sweat and by transpiration, which can evidently have no other agents,
though some authors have admitted that there were certain pretended
glands for the secretion of these fluids.

An infinite number of calculations has been made to ascertain the
quantity of fluid which the cutaneous exhalants usually pour out.
We are dismayed when we read the result of the labours of many
philosophers upon this point, when we go over the calculations,
enormously multiplied, of Dodard, Sanctorius, Keil, Robinson, Roye, &c.
To what do all these calculations, for which the life of a single man
would perhaps be insufficient, tend? To prove to us that when we start
from a false principle, the whole chain of consequences drawn from it
is false, though these consequences may be rigorously deduced from each
other. In fact, most philosophers have considered the skin as a kind of
fountain with numerous capillary tubes, always throwing out in the same
time the same quantity of fluids, and being able consequently to be
subjected, like inert capillaries which pour out fluids, to proportions
and calculations of quantity. But the results of these calculations
have soon proved how mistaken their authors were. Read these results,
and you will see that none of them agree, that frequently very great
differences characterize them. Is this astonishing? A thousand causes
make the transpiration vary at every instant. Temperament, exercise,
rest, digestion, sleep, watchfulness, the passions, &c. increase or
diminish the action of the cutaneous exhalants. I do not speak of the
difference from climate, seasons, &c. which is still more decided.

An attempt has even been made recently to ascertain, what belongs to
the urine, to the transpiration, to the pulmonary perspiration and
to the excrements, to calculate the relation which exists between the
quantities thrown out in these four ways; useless researches! We might
obtain from them results for one man, which would not be applicable
to others. Thus see if we have ever been able to make a single useful
application to physiology or pathology of all these immense labours
on transpiration. What would you say of a man who, during the days of
the equinox, in which the state of the atmosphere was every minute
changing, should try to establish proportions between the quantities of
rain which fell in every quarter of an hour, or of one who endeavoured
to fix relations between the quantities of fluids which are evaporated
in given times, from the surface of a vessel under which the intensity
of the heat which warmed the water varied every instant. The comparison
is just. We might be able to say in general, at the end of a given
time, nearly how many pounds of substances went from the body; and yet
this varies in every individual. But to attempt to say in a general
manner what, in this common quantity, the urine and transpiration
separately furnish, is to prove that we do not understand the nature of
the vital forces.

We have already observed, that all our knowledge upon the varieties of
transpiration, is reduced to some general data; that, for example, in
cold seasons and climates, it is by the internal emunctories that the
residue of nutrition and digestion principally passes off, whilst in
warm climates and seasons, it is the cutaneous organ that principally
throws it out.

The skin on the one hand, and the kidneys and pulmonary surface on the
other, are then in this respect, in a constantly inverse activity.
Physicians very well know this difference in regard to the urine and
sweat; they know that when one is increased, the other is diminished:
that in winter the urine contains principles of various kinds, and
that in summer the transpiration has a salt taste and other peculiar
characters which it owes to the substances which are foreign to it
in the first season. But they have not so well examined the relation
of the transpiration with the sweat; this determined me to make the
following experiments:

I wished to know what is the state of the respiratory fluid in
summer, in which there is much transpiration, and in which all the
heterogeneous principles consequently go out by the skin. To obtain
this fluid which is exhaled in insensible vapour, I placed a clean,
empty bottle in a pail filled with ice and the muriate of soda, and
I respired a long time in it, taking care not to allow any saliva to
fall in. The parietes, chilled by the external ice, condensed into
small icicles the vapour of my breath, on the internal surface of the
vessel. When I had made a certain quantity of these, I withdrew the
bottle; then by putting it into tepid water, the icicles immediately
melted, and I had in a liquid state my respiration, which was before
in vapour. Now I have been struck with two things in this experiment,
1st, with the small quantity of fluid that I was able to obtain, though
I had respired for an hour, and afterwards made two men respire each
an hour; 2d, with this, that most of the reagents have no action upon
this fluid. Nitric, sulphuric and muriatic acids, lapis infernalis,
and alkohol produce no effect when mixed with it. In evaporating a
small quantity in the concavity of a watch chrystal, no residuum is
left; placed in a spoon over the flame of a candle, it experiences no
alteration from the heat. In a word, I have been almost tempted to
believe that it was nothing but water. I confess however that this
experiment ought to be carefully repeated.

The little fluid obtained made me believe that the form of the vessel
was not well adapted to the purpose, because it did not present
sufficient surface and the vapour of the lungs was too little divided.
I took then the spiral cylinder of a small alembic which I surrounded
with ice in a pail; I made a man breathe through it, and I obtained
in fact more fluid, but infinitely less however than I expected,
considering the great cloud that is formed in winter by respiration.
In an hour, two ounces of fluid only were condensed, which I weighed
comparatively with water, and found a little heavier, a proof that some
principles are mixed with its aqueous portion, and with which I am
unacquainted.

I am convinced that in winter I should have condensed much more vapour;
the inspection of an animal that breathes proves it even, as I have
just said. I am persuaded also, that like the urine, the respiratory
fluid is then charged with principles which, during summer, pass off
by the skin, though I have not however any experimental data upon
this essential point, which I propose to clear up the approaching
winter. I think even that many colds depend upon this. In fact, many
of these principles thrown out by the mucous surface of the bronchia,
not soluble in the air, like their aqueous vehicle, stagnate upon this
surface, irritate and excite a cough which throws them off. On this
account, we cough much in winter, as we have often occasion to bathe
in summer, when the saline substances, which are accumulated upon the
skin by the exhalation that takes place there, cannot be evaporated by
the air. Hence why also in many affections of the lungs, in which the
mucous glands and the bronchial exhalants do not increase the quantity
of fluid they usually pour out, but only separate with it, on account
of their change of organic sensibility, substances which the air cannot
dissolve, hence, I say, why in these affections there is a constant
cough; for, as I have said, when a substance remains for any time upon
the mucous system, it irritates, and it makes an effort to get rid of
it. I believe that this elucidates the cause of many coughs, which
have been considered as nervous, on account of the small quantity of
expectoration, and which are only a means that nature employs to supply
the want of the evaporation of the air.

I think that physiologists have not paid sufficient attention, either
as it respects the bronchia or the skin, to the part which can be
evaporated, and to that which cannot. Some animals seem to throw out
more of these principles that cannot be evaporated, than man; hence
why it is necessary to curry horses every day, and even to bathe them
often, in order to cleanse their skins which the air would leave dirty.
Fourcroy and Vauquelin have remarked that there is never phosphate of
lime in the urine of these animals; this substance appears to pass out
with the sweat, and to be chrystalized on the surface of the skin, from
which it is removed by friction and water. I can hardly conceive how
the hairs can be the emunctories of it; it appears to me to be more
natural to think from analogy, that it is by the sweat that it escapes.
I presume that the rain, in the natural state is as necessary to these
animals as to plants. The first do not avoid it; many even expose
themselves to it; it serves as a bath for them, removes the saline
particles the air does not dissolve, and washes the skin.

The cutaneous exhalants do not appear to be everywhere equally
abundant. The face and chest contain many of them; we sweat easily in
these places. On the back and the extremities they are less numerous.
It is rare that we sweat on the palms of the hands and the soles of the
feet. Besides this varies remarkably in different individuals. I know
two sisters, belonging to a family in which phthisis has been frequent,
whose chests are however well formed, and who have never had any sign
of an affection of the lungs, and yet when they are warm they always
sweat from the chest. We know that in some the sweat appears most
usually in the face, and in others on the cranium.

Have the nerves any influence upon the cutaneous exhalation? In many
cases of paralysis, the patients sweat from the sound side. I have
attended, for two months past, a man at the Hôtel Dieu, who after
an apoplexy, had hemiplegia so that the left side of the body was
immoveable, and who only sweats from this side, so that an evident line
of demarcation is visible the whole length of the median line. On one
side the skin is dry, and on the other it is very moist. I know cases
are related in which opposite phenomena have taken place; but they do
not destroy the observation that is uniformly made, that the sweat
takes place equally upon the sound and the diseased side. Besides, who
does not know that when the nervous action is annihilated in a limb,
a blister acts upon it as usual? Do convulsions, in which the nervous
action is so much raised, increase cutaneous exhalation? Have the
states of extreme sensibility, in which all the cutaneous nerves are
so susceptible of receiving all impressions, the least known influence
upon sweating? Let us acknowledge then that in cutaneous exhalation, as
in secretion, we know nothing of the nature of the nervous influence,
if it does exist.


_Sebaceous Glands._

Besides the insensible transpiration and the sweat, which are thrown
out by the skin, this organ is constantly lubricated by an oily fluid,
which occasions, when coming out of a bath, the water with which it
does not unite, to collect in small drops upon the body, which greases
the linen when it remains too long in contact with the skin, catches
the dust that is floating in the air, makes, it remain upon the skin,
and retains many foreign substances coming with the sweat from without
or within.

This fluid is in general much more abundant in negroes, whose skin
is on this account disagreeable, than in European nations in whom
it abounds especially in places provided with hair, particularly
on the cranium. If left without dressing, the hair becomes greasy,
unctuous and shiny; it seems even that this abundance of oily fluid is
destined to support their suppleness. Thus art imitates nature in the
preparation of it, and greasy substances almost always enter into the
dressings of the toilet. It appears that there is less of this fluid in
other parts where there are hairs. It oozes in very small quantity from
the soles of the feet and the palms of the hands, no doubt on account
of the thickness of the epidermis. When we wash these last, the water
collects in small drops on the back of them, and not in the palms,
which are easily and uniformly wet; there is never any of it deposited
on the surface of the nails. This cutaneous oil, retained in certain
places, as in the axilla, the perineum, the folds of the scrotum, &c.
becomes mixed there with certain principles of the transpiration, and
often exhales a fetor that is almost insupportable.

This oily fluid, of the nature of which we know but little, is not
like the transpiration or the fat exposed to evident increase and
diminution; it is always found in nearly the same proportion. It
appears to preserve the suppleness of the skin, by preventing it from
cracking. The ancients sought no doubt to imitate its action over the
whole skin, as we imitate by pomatum its functions in regard to the
hair, by the oily unctions which they made upon the body. This we know
was much practised among the Romans.

Whence comes this cutaneous oil? It can be furnished from three
sources, 1st, from transudation; 2d, secretion; 3d, exhalation.

Some have thought that the sub-cutaneous fat oozed through the pores to
form it; but the scrotum which is destitute of this fat is one of the
most oily parts. The skin of the cranium, which is so to the highest
degree, is hardly at all fatty. That of the cheeks which covers much
fat, is scarcely lubricated with it, &c. In emaciation the skin is
often as unctuous as in corpulency, though it is not always the case.
Finally, in all the other functions, physical transudation is proved to
be nothing; would it exist then here alone?

Those who admit the secretion of the cutaneous oil, (and they are the
greatest number,) place the source of it in the small glands that are
called sebaceous, and which they say are every where spread under the
skin. We see some small tubercles upon the convexity of the ear, upon
the nose, &c. but in most of the other parts it is impossible to
distinguish any thing; we see only the small eminences of which I have
spoken and which make the skin rough; now they have nothing in common
with these glands, the existence of which I do not deny, but which I
confess I have many times in vain sought for.

This has made me think that there is perhaps an order of exhalants
destined to separate the cutaneous oil, and which is distinct from
that of the exhalants which throw out the transpiratory matter. There
is in the cellular texture exhalants for fat and others for serum.
Certainly no gland presides there over the secretion of the fat. It is
the same with the marrow which the exhalants of the medullary membrane
furnish. There is I think as much probability in the supposition of the
exhalation, as of that of the secretion of the cutaneous oil.

Besides, we must not confound this oil, either with that ceruminous
matter which certain glands pour out on the edges of the eyelids and
behind the ears, and which is forced out by pressure in the form of
little worms, or with that whitish substance that is collected between
the glans and the prepuce, and which is so evidently furnished by small
glands.


ARTICLE THIRD.

PROPERTIES OF THE DERMOID SYSTEM.


I. _Properties of Texture._

These properties are much developed in the skin. The alternations
of emaciation and corpulency through which our organs, the limbs
especially, pass sometimes from a determinate size to one double or
even treble, and afterwards return to their primitive state, prove
these properties; and so do all the different tumours, deposits of
pus, external aneurisms, sudden engorgements which accompany great
contusions, aqueous collections in the abdomen, pregnancy, scirrhi,
numerous affections which increase the size of the testicle, hydrocele,
&c. We see in all these cases the skin at first extended and dilated,
then contracting when the cause of the distension has ceased, and
occupying the place in which it was originally circumscribed.

The remarkable separation which the two edges of a wound experience,
that is made by a cutting instrument, is owing to the contractility
of texture. This separation which takes place upon the dead body,
proves what we have already often remarked, viz. that the properties of
texture, absolutely inherent in the organic texture, are foreign to the
vital forces from which they only borrow an increase of energy; thus
the cutaneous retraction is much stronger during life in a longitudinal
or transverse wound. But it is particularly in amputation that we
observe this increase of contractility from the vital action. No part,
not even the muscles retract so much as the skin; hence the precept so
much recommended in this operation of saving the integuments as much
as possible; hence the essential modifications that have been made in
the ancient methods. The muscular retraction is more sudden; but this,
which is more durable, ultimately prevails; so that in the ancient mode
of amputation, where every part was cut at the same level, they had a
conical stump, the summit of which was formed by the bone, in which was
next seen the muscles, arteries, &c. and in which the skin representing
the base, terminated on the side of the limb.

There are however many cases in which the dermoid extensibility is less
than it at first seems to be. For example, in large sarcoceles, the
skin of the neighbouring parts of the scrotum being drawn, is applied
upon the tumour, and makes up for the extensibility that is wanting in
the skin of this part; that of the penis especially is almost wholly
employed to cover the tumour; so that this organ disappears. It is to
the limits placed to the cutaneous extensibility that must also be
referred the following phenomenon; in a wound with loss of substance,
the fleshy granulations, in contracting by the evacuation of the
white substance that filled them, draw the neighbouring skin in order
to cover the wound; now this drawing produces not only an extension
but a real locomotion. Hence why when the skin, naturally tense and
adherent, cannot yield to this locomotion, the cicatrices are formed
with so much difficulty, as we see upon the cranium, the sternum, &c.
why on the contrary on the scrotum, the fold of the axilla, &c. they
take place with so little; why in dissecting out tumours, it is so much
recommended to save the sound integuments, &c.

When the skin is stretched, the fibres which compose the spaces that
have been spoken of, separate from each other, and these spaces become
broader. Their breadth becomes especially evident on the internal
surface of the dermis; for as all the pores of the external surface
pierce obliquely its texture, the distension of this texture only
diminishes the length of the small canal they form, but does not
enlarge the orifice of it; thus whilst the internal surface contains
interstices of considerable size, this remains uniform, but allows us
to see these interstices, which render it more transparent where they
exist; hence that appearance like marble on the skin of the abdomen of
women who have had many children.

When the skin is contracted, the internal spaces are drawn together
and even effaced. The external surface which has none of these, cannot
diminish so much in breadth, so that there is a disproportion in the
breadth of the internal and external surface; hence, as I have said,
the convexity of the latter in the horny hardening produced by boiling
water; hence also the inequalities and external roughness which
takes place when cold acts powerfully upon us, and which contracts
the dermoid texture. Besides, this phenomenon only takes place when
the contractility is evident in the ordinary state; for if there has
been previous distention, the cells already enlarged, return only in
contracting to their natural state, and there is no disproportion in
the extent of the internal and external surfaces of the skin.

In most of the extensions, there is a diminution of the thickness of
the dermoid texture. It is only when it is dilated by the infiltration
of water in its spaces, as in leucophlegmasia, that it increases in
thickness by diminishing in density. In chronic inflammation, in
engorgement, and in various alterations of which the dermoid texture is
the seat, it loses in part the faculty of stretching; it breaks with
ease when it is distended. This is what happens in some aneurisms,
in those of the aorta especially that have produced an absorption of
the sternum. A slow inflammation seizes upon the skin that covers the
tumour, and it breaks with a degree of distention infinitely below what
it bears in a sound state, if the death of the patient does not prevent
this fatal rupture, two examples of which I have seen in the ward of
lying in women at the Hôtel Dieu. In this state of inflammation, the
distention is very painful, whilst it is not so in the ordinary state.

The skin loses also its contractile power in most of the chronic
affections of which it is the seat, and which alter its texture.

Are there some days in which the skin is more contracted, and others
in which it is looser and more expanded? I believe so, from observing
the marks left after small-pox, which are much more apparent and deeper
some days than others.


II. _Vital Properties._

These are strongly marked in this system. We might say, that nature
by giving an excess of life to this dermoid covering, has wished to
establish a striking line of demarcation, and to make us perceive the
difference between the inorganic bodies with which its external surface
is in contact, and the organized textures that its internal surface
covers. I shall consider these vital properties as in all the other
systems; some belong to animal life and others to organic.


_Properties of Animal Life._

The animal sensibility exists in the highest degree in the skin. It
presides over the feeling, which is more acute and delicate there than
in most of the other textures. It is also the cause of touch, a double
function which is very different.

The feeling is the faculty of perceiving the impression of the
surrounding bodies. It gives us the sensations of heat and cold,
moisture and dryness, hardness and softness, &c. It has relation then,
1st, to the existence; 2d, to the general modifications of external
bodies. Its exercise precedes that of all the other senses which
cannot be exercised until after its action. It is necessary to the
sight, to hearing, smelling and the taste, as it is to the touch. It
depends only upon a particular modification of the animal sensibility;
it is nothing but this property considered in exercise. Thus when the
particular modifications of this sensibility which preside over the
other senses have been destroyed, when the eye is insensible to light,
the ear to sounds, the tongue to tastes and the pituitary membrane to
odours, these different organs still preserve the faculty of feeling,
both the presence of bodies and their general attributes.

The touch has only relation to the particular modifications of bodies;
it is the source of our notions upon their external forms, their
dimensions, size, direction, &c. It differs essentially from the four
other senses.

1st. In this, that it does not require, like the feeling, any
particular modification of sensibility. The hand is a little more
sensible than the rest of the skin; but there is not a great
difference, and we should touch bodies almost as well, if that of
the abdomen covered the phalanges. On the contrary, each sense has a
peculiar sensibility which places it exclusively in relation with a
determinate body in nature. The pituitary membrane would be struck by
light in vain, if placed at the bottom of the eye like the retina;
the palatine membrane if it lined the nasal fossæ, would not perceive
odours, &c.

2d. The touch is exercised only upon masses, more or less considerable
parcels. The other senses are brought into action by the insensible and
infinitely multiplied particles of bodies, as the luminous, savoury
particles, &c.

3d. Most of the other senses do not require the previous exercise of
the will. Odours, light and sounds strike upon their respective organs,
and often produce, without our attending to them, their respective
sensations. It is the same with feeling; the will most commonly has
no part in it. It is exercised because we live in the midst of many
excitements. We do not most often seek for the causes of general
sensations; they are those that come and act upon us. On the contrary,
the touch requires to be produced by an act of the will. It is exerted
in consequence of the exercise of the other senses; it is because we
have seen, heard or felt an object, that we touch it. We confirm or
correct by this sense the notions, which the others have given us.
Hence why it is, as it were, dependant on them. The more they are
contracted, the less frequently is it exercised. The blind, the deaf,
&c. have less desire to touch than him, who has all his sensitive gates
open to the impression of external bodies.

4th. Most of the other senses require a peculiar structure as well as a
peculiar sensibility in the organs which compose them. On the contrary,
the touch only requires a particular form in its organs. Provided that
these have on the one hand animal sensibility, and on the other can
embrace by many points external objects, they can distinguish their
tangible qualities. The touch will be obscure if we grasp bodies in
one or two directions only; yet it will take place. Thus we touch with
the hollow of the axilla, the bend of the arms, hams, &c. with the
lips and with the tongue. Thus the elephant touches with his trunk,
reptiles by twining themselves around bodies, most animals with their
snouts, &c. But the more the points of contact are multiplied, the more
perfectly is the sense exercised. The hand of man is in this respect
the most advantageously formed; it proves that he is better adapted to
communicate with what surrounds him than all other animals; that the
empire of his animal life is naturally much more extended than that
of theirs; that his sensations are more accurate, because they have a
means of perfection that theirs have not; and that his intellectual
faculties are destined to have an infinitely greater sphere, since they
have an organ infinitely better than theirs to perfect them.

The sensibility of the skin resides essentially, as we have seen, in
the papillary body; it is there that all the great phenomena relative
to sensation take place. It is this portion of the skin that truly
belongs to animal life, as the reticular body is, on account of the
vascular plexus that forms it, the portion essentially dependant on
organic life. The chorion being as it were passive, remains foreign to
every kind of important function, and serves only for a covering.

The extremely acute sensibility of the papillary body requires a
covering to defend it from strong impressions. This covering is the
epidermis. When it is removed, every touch is painful; the impression
of the air even is very much so; it is this removal of the epidermis
that produces the smarting that is felt when a blister is taken off.
Observe in fact that smarting is a very frequent kind of pain, which
the animal sensibility of the skin occasions when more raised than
usual. This term[1] is borrowed from burns, which, when they are only
to a certain extent, acting nearly like blisters, lay the papillæ bare;
now as it is always the skin which is exposed to the action of fire,
we transfer to all burnt organs the ideas which we attach to the word
smarting. But the pain is far from having the same character in the
other systems; this peculiar one belongs only to the dermoid, in which
it takes place from a burn, erysipelas, after a blister, &c. and during
all inflammations that have their seat in the reticular body. No other
system when inflamed gives us this sensation. The pain is throbbing
in the cellular; it exhibits a wholly different modification in the
muscular, when it is the seat of acute rheumatism, &c.

 [1] In order to understand this sentence it should be observed that
 the word which I have translated smarting is _cuisson_, which means
 the action of fire upon animal bodies, and is also used for the
 painful sensation which this action produces.—TR.

There is another kind of pain which is also peculiar to the cutaneous
system; it is itching, which is the first degree of smarting. We
remove it by a gentle friction, which exciting in the papillæ a
different sensation, effaces that of which they are then the seat;
but when this new sensation has passed off, the former one, which is
occasioned by a permanent cause, is reproduced and requires a new
friction; there happens then in a small way, what we observe in a
large one, when a stronger pain makes us forget one that is weaker. No
other system in the economy exhibits this kind of pain, so frequent in
itch, herpes and many other cutaneous eruptions. In their tubercular
inflammations, the serous membranes become the seat of white eruptions,
analogous to many of those of the skin; the mucous surfaces are also
often affected with many small pimples; now this sensation is never
manifested in either of them.

There is also a sensation which appears to be the minimum of that pain
of which smarting is the maximum; it is tickling, a mixed sensation,
an hermaphrodite, as an author has called it, which is agreeable when
carried to a certain degree and painful beyond it. Carry the fingers
lightly over a mucous or serous surface, a muscle or a nerve laid bare;
an analogous sensation will never arise from the contact.

The animal sensibility of the skin is, like that of the mucous
surfaces, subjected to the essential influence of habit, which can
transform successively into indifference or even into pleasure, what
was at first painful. Every thing that surrounds us furnishes constant
proof of this assertion. The air in the succession of the seasons,
caloric in the numerous varieties of the atmosphere, in the sudden
change from one temperature to another, water in a bath, in the moist
vapours with which the medium is loaded in which we live, our garments
of which some, as those of wool, are at first very painful, every
thing which acts upon the skin by mere contact, produces sensations
in it which habit continually modifies. Observe the mode of dress of
different nations; in some, all the superior extremities are bare;
in others, the fore-arm only appears; the inferior extremities,
either in whole or part, are naked in others; in some, a more or less
considerable portion of the trunk is left exposed to the air, and among
the savages, nothing is covered. The portions which in each people
remain naked, bear the contact of the air, without giving any painful
sensation. Let them expose, on the contrary, parts usually covered,
especially if it is cold, and at first pain will be the consequence of
it; then the parts gradually becoming accustomed to this contact, will
get to be insensible to it. There has been much said latterly of the
danger of the Grecian costumes, of the nudity of females, &c. I do not
speak of the morality of them; but every thing that is reprehensible
physiologically is, that the progress of the fashion has been more
rapid than that of the sensibility. If they had exposed at first the
neck, then a little of the chest, then the bosom, &c. habit would by
degrees have given a new modification to this property, and no accident
would have resulted from it. But in going suddenly from a costume in
which every part is covered, to that in which the superior half of the
chest, either before or behind, remains naked, is it astonishing that
colds, catarrhs, &c. should be the result of it?

Habit extends its empire, in relation to the skin, even to our manners
themselves. Decency is in this respect a thing of comparison. An Indian
woman, with nothing but a narrow cloth around the pelvis, would be with
us an object at which the public modesty would be shocked. The habit
of mankind serves her as a veil in her own country. A female savage
transported entirely naked to the same country, would be indecent
there; she is not so in her own. Observe our fashions in their rapid
succession; a woman, who by not changing her costume, would have had
two years since, that of a courtezan, would now find herself dressed
with great modesty. Indecency in costume is that merely which shocks
our habit. The female Indian, with the rag that covers only a quarter
of her body, is more decent than the woman in whom a small opening
separated the neck-handkerchief in our old fashions. The sight of the
face shocks those people among whom females are veiled. Let us consider
then habit as the type of the decency of costumes. Nature has wished in
physiology, that the phenomena over which it presides, should be slowly
connected; it is the same in morals. The woman who suddenly changes her
dress from one that is close to one that is not, exposes herself to
painful sensations, to catarrhal diseases, &c. and shocks the eyes of
those who had been accustomed to see her in a different exterior. When
the change is gradually and insensibly brought about, neither health
nor morals are affected.

Habit does not modify the cutaneous sensibility which arises from an
alteration of texture, from an inflammation, &c. Powerfully raised in
this last state, it is much above its natural level. Then the least
contact becomes extremely painful; thus the skin is no longer then in
a state to exercise the sense of feeling. The touch itself does not
distinguish general sensations. All bodies make a common and uniform
impression, it is that of pain.

The animal sensibility of the skin sometimes diminishes and even
disappears; paralysis is a proof of this. These affections, more rare
than the loss of motion, often however take place. In the organs of
the senses, it is the eye which most frequently loses the sensation;
the ear comes next, then the skin, then the nostrils and finally
the tongue, which is the sensitive organ that is always most rarely
paralyzed, no doubt because it is that which is the most connected
with the support of organic life, without which we could not exist.
The others belong especially to animal life, which we can lose in part
without ceasing to exist.

The whole skin is never at the same time paralyzed; there is rarely
even hemiplegia in this respect; the feeling is not extinguished but in
an insulated part. I would remark that the existence of these paralyses
is also a proof of the want of nervous influence upon cutaneous
exhalation and the capillary circulation, since both go on very well in
this case as well as in paralysis of motion, as I have observed above.
Cut the nerves of a limb of an animal, in order to render this limb
insensible; if after this you apply an irritant, the skin will inflame
as usual.

When the animal sensibility is in exercise, is there a kind of erection
of the papillæ that they may feel more acutely? The same observation
may here be made as was in regard to the mucous surfaces. This erection
is an ingenious idea of some physicians, and not a fact which rests
upon observation. I even think that this contradicts it; for examined
with a glass the papillæ appear to be constantly in the same state. Why
should not the skin feel like a nerve laid bare, like the eye, the ear,
&c. in which these sorts of erections have never been imagined?

Animal contractility is wholly foreign to the cutaneous organ, which
moves voluntarily only by the influence of its fleshy pannicle.


_Properties of Organic Life._

Organic sensibility and insensible contractility exist in the highest
degree in the cutaneous organ. The external capillary system, which
forms the reticular body, is, as I have said, especially the seat of
these properties. They are in constant activity in order to preside,
1st, over the capillary circulation; 2d, over exhalation; 3d, over
absorption; 4th, over the nutrition of the whole dermoid texture;
5th, over the secretion of the cutaneous oil, if the sebaceous glands
exist. It is not astonishing that these properties should be so
much developed in the skin, in which they have so many functions to
support. Add to these considerations the constant action of external
bodies, an action which keeps this organ in continual excitement, which
incessantly stimulates its sensibility, which is to this sensibility
what that of the bodies contained in the mucous surfaces is to the
sensibility of these surfaces; the irritation is even more sensible,
because the stimuli are oftener changed. A thousand agents of nature,
of different density and composition continually succeed each other on
the exterior of the body, and at the same time that they act upon the
animal sensibility of the skin, to produce various sensations, they
excite the organic sensibility in order to support the functions over
which this sensibility presides.

Is it astonishing then that the greater number of cutaneous diseases
supposes an alteration in this property and in the insensible organic
contractility which is not separated from it? I divide these diseases
into four classes, according to the structure we have distinguished in
the skin.

1st. There are diseases of the papillæ; these are the paralyses and
various kinds of increase of feeling, which reside only in the nerves.
Women are especially subject to these last, which are so great in some
nervous affections, that mere contact of the skin if considerably
powerful produces convulsions. To this also should be referred the
extreme susceptibility of some individuals in whom tickling produces a
general revolution. It is necessary to distinguish these exaltations
of animal sensibility, from those of which we have spoken above, and
which depend upon inflammation. The organic sensibility is especially
affected in these last; we might say that by its increase it is
transformed into animal sensibility; whereas in the other case this
last property alone is altered.

2d. There are diseases which have evidently their seat in the cellular
texture which occupies the dermoid spaces; such are the inflammations
of the cutaneous portion which covers a phlegmon, a bile, &c.

3d. There are diseases of the external capillary net-work, from which
the exhalants arise. To this must be referred erysipelas, many species
of herpes, measles, scarlatina and many acute cutaneous eruptions that
are daily met with in practice.

4th. Finally, there are diseases in which the chorion is affected.
Elephantiasis, and in general many chronic cutaneous diseases appear
to me to be of this number, and I will even observe that the chorion
never appears to be primarily affected in acute diseases. The
obscurity of its vital forces, its dense and compact texture, and its
comparative want of vessels prevent it from accommodating itself except
to chronic affections. In phlegmonous erysi pelas, in biles, &c. it
is only influenced, but it is not essentially diseased. Thus we have
seen that all the affections of the osseous, cartilaginous, fibrous,
fibro-cartilaginous systems, &c. are really slow and chronic, on
account of the texture and the vital obscurity of these systems.

Now if we reflect on this division of cutaneous diseases, we shall see
that except those of the first class, which are not numerous and which
consist in greater or less alterations of animal sensibility, we shall
see, I say, that all the others suppose a more or less considerable
affection of the organic sensibility and of the corresponding
insensible contractility. All are derived from an increase, a
diminution or an alteration of these properties.

It is also to the different changes of these properties, that must be
referred the more or less copious sweats and the various exudations
of which the skin is the seat. In fact, the exhalant vessels remain
always the same in relation to their structure. Why then do they admit
a greater or less quantity of fluids? Why at certain times do they
allow of the passage of substances, which they repel at others? It is
because the modifications of their organic forces are changed. These
forces are often weakened in an evident manner in diseases; they become
languid and are prostrated. Then blisters are applied in vain; the
organic sensibility no longer answers to the excitement that is made
upon it. This is a striking phenomenon in ataxic fevers, and proves
the independence of the phenomena of cutaneous exhalation, capillary
circulation, &c. in regard to the cerebral nerves. In fact, whilst
during the paroxysm the brain is in extreme excitement, the voluntary
muscles are put by this excitement into a violent state of convulsion,
and the energy of the whole of the animal life seems to be doubled
before it ceases to exist, the organic is already in part exhausted;
the functions of the portion of the skin which belongs to this life
have already ceased.

The stimuli of cutaneous organic sensibility vary remarkably in their
degree of intensity. 1st. The strongest are fire, cantharides, the
alkalies, the acids sufficiently diluted by water not to act but upon
the vital forces and not to alter the dermoid texture by the horny
hardening, the juices of many acrid and corrosive plants, certain
fluids even produced in the economy, as those of cancers, &c. All these
stimuli redden the skin when they are applied to it. 2d. Most of the
same stimuli, diminished in intensity, stimulate it but slightly. 3d.
Finally, aqueous fluids, cataplasms and emollient fomentations seem
to produce this excitement the least; they even rather weaken the
cutaneous organic sensibility; they seem to act upon it like sedatives
and moderate the kind of excitement it produces in inflammations.
The same is true of most of the fatty substances; thus oils, butter,
grease, &c. are in general not calculated to keep up the suppuration
of blisters. It is requisite, in order to keep the skin at the degree
of organic sensibility, necessary for the purulent exudation that then
takes place, to mix cantharides with fatty substances.

The skin does not appear to enjoy sensible organic contractility.
Stimuli usually produce no other action upon it, than the contraction
imperceptible to the eye, which composes insensible contractility, and
which takes place especially in the small capillary vessels. There is
however one circumstance in which this contraction is, to a certain
extent, apparent; it is when cold acts briskly upon the skin, which it
wrinkles into goose flesh, as it is called. I have pointed out above
the mechanism of this contraction, of which the chorion is the seat,
and which holds a medium, like many motions which I have already had
occasion to notice, between the two species of organic contractility.


_Sympathies._

We shall still follow the division of the sympathies into active and
passive, a division which is more remarkable here than in most of the
other systems, because the sympathies are much more numerous.


_Passive Sympathies._

The animal sensibility is very often brought into action in the skin,
by the affections of the other systems. We know that the application
of cold to the sole of the foot frequently produces affections of the
head; that in many cases, the different species of itching, and even of
smarting appear without an injury of the part where the pain is felt.
It is useless to cite examples that are known to all physicians. I will
confine myself to the sympathies of heat and cold alone, which have not
yet been spoken of.

I call by this name the sensation that is experienced upon the skin,
when there is not a superabundance or absence of caloric there. There
is evidently a material cause for the heat in inflammation and for the
cold in the ligature of a great artery. On the contrary, in the cases
of which I spoke, it is but an aberration of the internal sensitive
principle, which resembles that which takes place when we refer the
pain to the extremity of an amputated limb. This is what occurs in many
cases of shivering, in which the internal sensitive principle refers to
the skin a sensation of which the cause does not exist. By approaching
the fire then we do not become warm, because we really were not cold;
but we only destroy by a real sensation, the opposite sensation which
is illusory that we experience, or rather we turn the perception from
this sensation. We know that at the instant of the ejaculation of
semen, a sudden and sympathetic chill often extends over the body.
We know the cold of fear, which almost always arises, like the sweat
produced by this passion, from the sympathetic action exerted upon the
cutaneous organ by an epigastric organ affected by the passion.

Observe what takes place in the beginning of most acute local diseases,
as in those of the serous and mucous surfaces, of the lungs, of
the gastric viscera, &c. &c. The organ which is to be the seat of
the disease is at first affected; immediately many sympathetic and
irregular symptoms arise in all those which are sound; this is the
affection that precedes. When the disease is once developed, and
it follows its periods, a new order is established, as it were, in
the economy. The relations of the organs seem to change. In the
preternatural irregularity of the functions, a kind of regular
assemblage of symptoms is manifested, it is this assemblage which
characterizes the disease and distinguishes it from every other in
which a different order of morbific relations is established between
the functions; now the passage from the natural to the preternatural
relation of functions is marked by a thousand vague symptoms,
which should be attributed to sympathies, and among which appears
particularly the kind of shiver in of which I have spoken.

In the beginning of digestion a kind of sympathetic cold is also
referred to the skin, which is most often as warm as usual; it is
an action exerted by the stomach upon the cutaneous sensibility, an
action from which arises a particular sensation, different no doubt
from that which the same viscus, when disordered, produces in the head,
occasioning head-ache, but which is owing however to the same principle.

The heat is very often sympathetic in the cutaneous organ, less
however, as I have observed, than in the mucous system. We know the
flushes of heat that so often extend over the skin in an irregular
manner, in different fevers, and which are not attended with a greater
disengagement of caloric.

Our modern philosophers will not perhaps be able to understand, how
it is that whilst in the greatest number of cases, the application of
a degree of caloric superior or inferior to that of our temperature,
is necessary to produce heat or cold, this sensation can arise in a
part though it may not have experienced an increase or diminution
of this principle. But in the greatest number of cases has not pain
a material cause? And yet all sympathies produce it without this
cause. The vulgar, who stop at the diversity of the modifications
of feeling, believe that an insulated principle presides over each.
Let us disregard all these modifications, in order to see but a
single principle in the irregularities as in the regular course of
sensibility. That this property, sympathetically altered, gives us
the sensation of heat or cold as in the skin, of pulling as in the
nerves, of lassitude as in the muscles in the beginning of a disease,
&c. these are but varieties of a single cause, one, of which we are
ignorant, but which evidently exists. In general, the sympathies of
animal sensibility put into action in each system the sensation which
is usual there. The sympathy which, acting upon the skin, creates there
a sensation of heat or of cold, would have produced that of lassitude
if it had acted upon a muscle.

In order to form an exact idea of heat and cold considered as
sensations, let us recollect that they may arise from different causes.
1st. From the increase or diminution of the caloric of the atmosphere.
2d. From the disengagement or the want of disengagement of this fluid
in a part of the economy, as in a phlegmon or after the ligature of
an artery of a limb. 3d. Sometimes without previous inflammation more
caloric is disengaged in the whole body; there is a general increase of
temperature; we then feel an internal and external heat; or caloric is
disengaged locally in a part of the skin, and the patient feels a heat
there as he does who applies his hand upon this place. 4th. Finally,
there are sympathies of heat and cold. Some other parts, besides the
mucous surfaces and the skin, feel these sympathies; we know the
sensation of coldness that is felt to arise from the abdomen to the
thorax, &c.

The organic properties of the skin are also frequently put into action
by sympathies. The sweat on the skin is suppressed in a moment, if a
cold body is taken into the stomach. The entrance of teas into this
viscus, and an increased cutaneous exhalation, are two phenomena that
take place almost at the same instant; so that we cannot refer the
second to the absorption of the drink, then to its passage into the
black blood through the lungs, and afterwards into the red blood. The
production of sweat is then here analogous to its suppression in the
preceding case; it resembles that of fear, and that of phthisis in
which the lungs being affected act upon the skin. Shall I speak of
the innumerable varieties of this organ in diseases, of its dryness,
its moisture, its copious sweats, &c. phenomena for the most part
sympathetic, and which arise from the relations which connect this
sound organ with the diseased parts? I have pointed out those which
exist between it and the mucous surfaces. The membrane of the stomach
is the one with which it especially sympathizes. The digestive
phenomena are a proof of this. It would be necessary to treat of all
diseases in order to speak of the sympathetic influences exerted upon
the skin. These influences are often chronic. How in many organic
diseases, do different tumours form upon the skin? Precisely as
petechiæ, miliary eruptions, &c. are produced in acute fevers; the
difference is only in the duration of the sympathetic phenomena.

Animal and sensible organic contractility cannot be evidently put into
action in the passive sympathies of the skin, since it is not endowed
with these properties.


_Active Sympathies._

The four classes of cutaneous affections of which we have spoken,
occasion many sympathetic phenomena, the following are some of them.

1st. Whenever the papillæ are strongly excited, as in the tickling
of very sensitive people, various organs feel it sympathetically;
sometimes it is the heart; hence the syncopes that then take place;
sometimes it is the stomach; thus I knew two persons who could be made
to vomit by tickling them; sometimes it is the brain, as when in very
irritable people, tickling is carried so far as to produce convulsions,
which is not very rare in nervous women. Who is ignorant of the
influence which the organs of generation receive from the skin, when
stimulated in different parts?

Physicians are often astonished at the extraordinary effects which
some mountebanks produce in the economy, who know how to profit by
their knowledge of the cutaneous sympathies produced by tickling.
But why should we be more astonished at these phenomena, than at
the vomitings produced by an affection of the womb, at the diseases
of the liver arising from an injury of the brain, or at hemicrania
the seat of which is in the gastric viscera? The only difference
is that we can in the first instance, produce to a certain extent
those sympathetic phenomena, which we only observe in the other. Why
do we not oftener make use in medicine of the influence which the
skin when tickled exerts upon the other organs? In hemiplegia, in
adynamic, ataxic fevers, &c. who knows if the excitement of the sole
of the foot, which is so sensible, as every one knows, if that of the
hypochondrium, which is not less so in some people, &c. would not be
better, if repeated ten or twenty times a day, than the application of
a blister, the irritation of which soon passes off? Besides you would
never obtain by a blister, rubefacients, &c. means which act as much
and more upon the organic than the animal sensibility, an effect as
striking, an affection as general in the sensitive system, as by the
tickling of certain parts, a means, which acting only upon this last
species of sensibility, produces phenomena exclusively nervous; whilst
the exhalant system and the capillary with red blood are especially
affected by the others. Certainly there are cases in which one of these
means is preferable to the other. I propose to ascertain these cases.

We have not yet sufficiently analyzed the different kinds of excitement
in diseases; we have not endeavoured to profit enough by what
observation has taught us, upon the sympathies we can produce at will.
Might we not however say, that nature has established certain relations
between very remote organs, that we may be able to make use of these
relations in our means of cure? The charlatan, who employs external
tickling for certain nervous affections, is often more rational,
without knowing it, than the physician with all his pharmaceutical
means.

2d. Whenever the cutaneous exhalants or the external capillary system
from which they arise, are affected in any manner, many other parts
feel it, and this is a second order of the active sympathies of the
skin. Here are referred a great number of phenomena, of which the
following are a part.

A bath which acts upon the skin during digestion, affects
sympathetically the stomach, and disturbs this function. When this
viscus is agitated by spasmodic motions, oftentimes the influence which
it receives from it suddenly calms it, and brings it to its ordinary
state. Not long since in my evening visit at the Hôtel Dieu, I saw a
woman who was vomiting continually from a sudden suppression of her
catamenia. I directed sedatives which were useless. The next evening
she was in the same state; I had her put into a bath; every thing was
calmed the moment she came out of it, and yet the catamenia did not
return. Few organs are more dependant on the skin than the stomach.

The action of cold upon the cutaneous organ produces many sympathetic
effects, especially when this action takes place while we are sweating.
The term repercussion of transpiration is not proper to express what
then takes place; it gives a very inaccurate idea. Let us suppose that
a pleurisy arises from cold suddenly applied, the following is what
happens; the organic sensibility of the skin being immediately altered,
that of the pleura is sympathetically altered. By it the exhalants
become in relation with the blood; they admit it instead of the serum
which they before received, and inflammation supervenes. Thus this
phenomenon is the same as that in which the application of a cold body
upon the skin suddenly arrests uterine, nasal hemorrhage, &c. &c. the
result only differs. Now in this last case, no one ever supposed that
there was a repercussion of fluid. The suppression of the transpiration
is a thing purely accessory and foreign to the internal inflammation
which takes place. When the skin sweats in summer, the vital forces
are more raised by the caloric which penetrates it; in this state, it
is more capable of acting sympathetically upon the forces of the other
systems. Hence why all strong stimulants that act upon it are more to
be feared then. It is so true that it is not the suppression of the
sweat which is dangerous, but the alteration of the vital forces of
the skin which sweats, that many kinds, as the sweat of phthisis, are
not so injurious when they cease for a time; they are checked even
with much more difficulty, because they are not produced by a cause
acting immediately upon the skin. Now if there was a repercussion of
the transpiration, every species of sweat that was suppressed would be
injurious. We never hear of a peripneumony arising from a suppression
of sweat produced by fear, rheumatism, &c. There would be then also a
repercussion of mucous matter, when a pleurisy arises from swallowing
a glass of cold water. Men judge only by that which is striking. The
suppression of the sweat is an effect like inflammation of the pleura,
but it is not the cause of it. If there was no sweat the instant the
cold was applied to the skin, inflammation would nevertheless come on.
In wounds of the head, with abscesses of the liver, &c. there is no
repercussion of fluids.

The trembling of which the voluntary muscles become the seat, the
debility of the pulse which the weakness of the action of the heart
produces, &c. are phenomena which the influence of the skin affected by
cold alone causes. In fact, only this organ, the commencement of the
mucous surfaces and all of that of the bronchia, are made cold by the
external air; all the others remain at their usual temperature.

We know the innumerable phenomena which arise from the disappearance of
herpes, the itch, &c. imprudently produced; in all these cases it does
not appear that the morbific matter is carried to the other organs,
though I do not pretend that this never happens. It is the vital forces
of these which are raised and which then occasion different accidents;
now as these forces vary in each system, these accidents will be
essentially different; thus the same morbific cause disappearing from
the skin, will produce vomiting if thrown upon the stomach, in which
the sensible organic contractility predominates; pains, if it goes to
the nerves which are especially characterized by animal sensibility;
derangements of sight, hearing and smell, if it affects the respective
viscera of these senses; hemorrhage, catarrhs, phthisis, tubercular
inflammation, &c. if it attacks the mucous surfaces, the lungs, the
serous membranes, &c. in which the organic sensibility is much raised.
Now, if the same morbific matter carried upon these different organs,
produced these accidents, they ought to be uniform. Do not their
varieties, and especially the constant analogy which they have with the
predominant vital forces of the organs in which they appear, prove,
that they depend upon the cause which I have pointed out?

We know that the serous surfaces and the cellular texture on the one
part, and the skin on the other, are often in opposition in diseases.
There is no sweat when dropsies are formed; the dryness of the skin is
often even more remarkable than the small quantity of urine, &c.

3d. When the cellular texture contained in the dermoid spaces is
inflamed, as in phlegmonous inflammation, in biles, in some malignant
pustules, &c. there comes on many sympathies which can be referred to
those of the general cellular system, which have been already noticed.

4th. The affections of the chorion itself, all marked with a chronic
character, on account of the kind of vitality and structure of this
portion of the skin, occasion also sympathies which have the same
chronic character, but of which we know but little.

The organic contractility cannot be put sympathetically in action in
the skin, as it does not exist there.


_Characters of the Vital Properties. First Character. The Cutaneous
Life varies in each organ._

Though we have spoken in general of the vital properties of the skin,
they are far from being uniform or at the same degree in all the
regions.

1st. There is no doubt that the animal sensibility of the soles of
the feet and the palms of the hands is greater than that of the other
parts. Many persons are so sensible in the hypochondriac region, that
the least tickling there produces convulsions. The anterior and lateral
part of the trunk is always more sensible than the region of the back.

2d. The organic properties do not vary less. The extreme susceptibility
of the face to receive the blood, is a proof of it, as I have said. It
is generally known that some parts are more proper than others for the
application of blisters. Observe on this subject that the places where
the animal sensibility predominates, are not the same as those in which
the organic is in the greatest proportion. The soles of the feet and
the palms of the hands hold the first rank in relation to one, and the
face in relation to the other.

In diseases we also see these varieties. Who does not know that some
particular parts of the skin are especially the seat of some particular
cutaneous affections, and that when these affections are general, they
always predominate in certain places. We ought not to be astonished
at these varieties, since we have seen that the dermoid texture is
infinitely variable as it respects its papillæ, its reticular body, its
chorion, &c.


_Second Character. Intermission in one relation; continuity in another._

The life of the cutaneous system is essentially intermittent in
relation to animal sensibility. All the senses exhibit this phenomenon.
Thus when the eye has for a long time gazed upon objects, the ear heard
sounds, the nose received odours, and the mouth tastes, these different
organs become unfit to receive new sensations; they become fatigued,
and require rest to regain their forces. It is the same with regard to
feeling and the touch; wearied by the impression of surrounding bodies,
the skin requires an intermission of action to regain excitability
adapted to new impressions. We know that a short time before sleep,
external bodies produce but an obscure sensation upon it, and that
their contact has no effect in this state, in which animals seem
to lose half of their existence. The more powerfully the cutaneous
sensibility has been excited, the more profound is sleep; hence why
all painful exercises, great frictions, &c. are always followed by a
deep sleep. Yet this sense can sometimes exert itself, while the others
sleep; pinch the leg of a man asleep; he draws it away without waking,
and has afterwards no remembrance of the sensation. Thus somnambulists
often hear sounds, even eat, &c. for, as I have said elsewhere, sleep
may affect but a very limited part of animal life, as it may the whole.

Under the relation of organic sensibility, the life of the cutaneous
system is essentially continuous. Thus the functions over which this
property presides have a character opposite to the preceding. The
insensible transpiration takes place continually, though there may be
some periods in which it is more active than in others. The oily fluid
is incessantly carried away and renewed; we might even say sometimes
that it is when the animal sensibility is interrupted, that the
organic is in the greatest exercise.

It is especially in diseases that they have made this observation,
which is besides generally applicable to organic life. All this life
is as active and even more so during the night than during the day.
Most of the diseases that attack the functions which belong to it, are
marked by an increase of activity during the night. All fevers which
particularly affect the circulation have their exacerbation towards
night. In diseases of the heart, the patients are more oppressed at
this period, &c. In phthisis which affects respiration, it is in the
night especially that there is hectic fever, sweats, &c. Pneumonia and
pleurisy, exhibit frequent exacerbations towards night. In glandular
diseases, either acute or chronic we make the same observation. It
would be necessary to refer to almost all the affections which alter
especially an organic function, in order to omit nothing upon this
point. On the contrary, observe hemiplegia, epilepsy, convulsions,
various paralysies of the different organs of sense, most mental
alienations, apoplexy and other affections which exert their influence
more particularly upon animal life, they have not, so often at least,
their exacerbations towards evening and during the night, no doubt
because in the natural state, this life is in the habit of becoming
drowsy and not of being raised like the other which seems to imprint
this character upon its alterations. Other causes no doubt have an
influence upon this phenomenon; but I believe this to be a real one.


_Third Character. Influence of the Sexes._

The sex has an influence upon the cutaneous life. In general the animal
portion of this life is more raised in women, in whom every thing that
belongs to the sensations is proportionally more marked than in man,
who predominates by the power of his locomotive muscles. The effects
of tickling are infinitely more powerful in females. All the arts which
require nicety and delicacy of touch are advantageously cultivated
by women. The peculiar texture of the chorion, a texture generally
more delicate, has no doubt an influence upon this phenomenon. As to
the organic portion of the cutaneous life, the difference is not very
great. Man appears to be superior in this respect; he generally sweats
more; his skin is more unctuous, which proves a greater secretion.


_Fourth Character. Influence of Temperament._

The temperament peculiar to each individual is not a less real cause
of differences in the skin. We know that the colour, roughness and
pliability of this organ vary according as individuals are sanguineous,
phlegmatic, &c. that these external attributes are even a character of
the temperaments. Varieties of structure no doubt coincide with these.
Is it then astonishing that the animal sensibility differs so much,
that the touch itself should be delicate in some and dull in others,
that some should be very ticklish, whilst others are not so at all,
&c.? Ought we to be astonished if the organic sensibility, which is
very variable, should determine, according to the individuals, many
varieties in the phenomena over which it presides; if in some, it
allows much blood to go to the face, and if it repels this fluid in
others who are always pale; if some men sweat much, whilst others have
the skin almost always dry; if the cutaneous oil varies in quantity;
if there are some skins much disposed to eruptions, either acute or
chronic, to pimples of different natures, and if others are almost
always free from them, even when the individuals expose themselves to
the contagion of these diseases; if superficial wounds, of the same
extent and made by the same instrument, are sometimes quicker and
sometimes slower in healing; if the cure of cutaneous diseases is also
very variable in its periods, &c. &c.?


ARTICLE FOURTH.

DEVELOPMENT OF THE DERMOID SYSTEM.


I. _State of this System in the Fœtus._

In the first periods after conception, the skin is but a kind of
glutinous covering, which seems to be gradually condensed, forms a
transparent envelope, through which we see in part the subjacent
organs, the vessels especially, and which is torn by the least jar.
This state continues for a month and a half or two months. The
consistence constantly increasing, soon gives to the skin an appearance
more nearly like that which it has in infants after birth. Its delicacy
is extreme at this period. It has not one quarter the thickness of
that of the adult. The moment in which it begins to lose its mucous
state appears to be that in which the fibres of the chorion are formed.
Until then the cellular texture and the vessels especially composed
it, and as the first is abundantly filled with juices during the early
periods, it is not astonishing that it should then give way under the
least pressure. But when the fibres are formed, the cellular texture
diminishes on the one hand, and is concentrated in the spaces that are
developed, and on the other the dermoid fibres, more dense than its
layers, increase the resistance.

We do not see upon the external surface of the skin of the fœtus most
of the wrinkles of which we have spoken above. Those of the face in
particular are not seen; the kind of immobility, in which the facial
muscles are, is evidently the reason of it. The forehead, the eyelids,
the edges of the lips, &c. are smooth. Besides, the abundance of fat
which then distends the integuments of the cheeks, prevents every
species of fold there. As the hands and the feet are found in part
bent at their articulations, by the attitude of the fœtus, different
wrinkles are already formed about these articulations, principally on
the hand, where however they appear less in proportion than afterwards.
The curved, papillary lines are not very evident on the foot and the
hand, even when the epidermis is removed.

The internal surface of the skin is remarkable for the slight adhesion
of the subjacent cellular texture, the cells of which filled with
fatty particles are removed with great ease, by scraping this surface
with the edge of a knife. We see then there the spaces already well
formed, and as distinct in proportion as afterwards. By pursuing their
dissection from within outwards, we insensibly lose sight of them
towards the external surface where the skin is condensed.

More blood enters the skin of the fœtus, than at any other period of
life. It is easy to observe this in small animals taken alive from
the womb of their mother; for in the fœtuses that are dead at birth,
or born prematurely, the cause which destroys life, increasing or
diminishing in the last moments the quantity of cutaneous blood,
prevents us from drawing any conclusion as to the ordinary state by an
inspection of them. The nerves are, as in all the other parts, more
evident; but the papillæ, though sensible, as I have said, have not a
proportionable increase.

The animal sensibility is not in exercise in the skin of the fœtus, or
at least it is very obscure there. This is owing to the absence of the
causes of excitement. These are the surrounding heat, the waters of
the amnios and the parietes of the womb, which can furnish materials
for sensations; but as these causes are always uniform, and have no
varieties, the fœtus can have but a very feeble perception, because
acuteness of sensation requires change of stimuli. We know that heat
long continued at the same degree becomes insensible, that a long
continuance in a bath takes away almost entirely the sensation of the
water, because habit is every thing as it respects sensation; nothing
but what is new affects us powerfully.

Is the organic sensibility of the skin in activity in the fœtus?
does it preside over the alternate exhalation and absorption of the
waters of the amnios? This is not the common opinion, it is not even a
probable one; but this question is far from being settled in so precise
a manner as many other points of physiology.

Besides, it cannot be doubted that there is a copious secretion of an
unctuous and viscid fluid, which covers the whole body of the fœtus,
but which is more abundant in some places than others, as behind the
ears, in the groin, the axilla, &c. either because it is secreted there
in greater quantity, or accumulated on account of the arrangement of
the parts. Accoucheurs have it wiped off after birth, and the females
of animals remove it by the repeated application of their tongues to
the surface of the body. This fluid appears to be to the skin of the
fœtus what the oily fluid is to that of the adult; it defends this
organ from the impression of the waters of the amnios. If the sebaceous
glands exist, it would appear that they furnish it, for it is certainly
from a different source from the sweat. When care has not been taken
to remove this covering, it irritates the skin, and may produce
excoriations, and a species of erysipelas. The air cannot remove it
by solution. Nothing similar oozes from the skin of the infant after
birth. Is it because the black blood alone is capable of furnishing the
materials of this substance?


II. _State of the Dermoid System during growth._

At the moment of birth the dermis experiences a sudden revolution.
Hitherto entered only by black blood, it is at the time the fœtus is
born, more or less coloured by it. Some fœtuses come wholly livid,
others are paler; there is a remarkable variety in this respect. But
all, shortly after they have respired, become more or less decidedly
red. It is owing to the arterial blood which is formed and succeeds
the venous blood that circulated in the cutaneous arteries. In this
respect the state of the skin is in general an index of what goes on
in the lungs. If an infant remains a long time of a violet colour, he
either does not breathe or breathes with difficulty. The extremities of
the hands and the feet in general become red the last. They are those
in which the lividity consequently continues the longest, when this
lividity is very evident. The blood which goes to the cutaneous organ,
enters it in general in a very uniform manner; the cheeks do not appear
to receive more of it in proportion. The sudden excitement it brings to
the organ, raises its vital forces and renders it more fit to receive
the impressions, which are new to it, of the surrounding bodies.

Observe in fact that a thousand different agents, the surrounding
temperature, the air, dress, the fluid in which the fœtus is washed,
the tongues of those quadrupeds who lick their young, carry to the skin
an excitement which is so much the more felt by the fœtus, as it is
not accustomed to it, and as there is an essential difference between
these stimuli, and those to which it had been previously subjected.
It is then that the remarkable sympathy which connects the skin with
all the other organs, becomes especially necessary. Every thing within
soon perceives the new excitements that are applied without. It is
these excitements, those of the mucous surfaces at their origin and
those of the whole of the bronchia, which especially bring into action
many organs hitherto inactive. There happens then, what is observed in
syncope, in which respiration, circulation, the cerebral action and
many functions suspended by the affection, are suddenly roused up by
external friction, by the irritation of the pituitary membrane, &c. The
phenomena are different, but the principles from which they are derived
in both cases are the same.

Then the organic sensibility is also raised. Transpiration is
established. The skin begins to be an emunctory of different
substances, which it did not before throw out; it becomes also capable
of absorbing different principles applied to its surface. The skin
of the fœtus is hardly ever the seat of any kind of eruptions; then
pimples of different kinds frequently appear.

All the parts of the cutaneous organ do not however appear to be raised
to the same degree of organic sensibility. For a long time after birth
the skin of the cranium appears to be the centre of a more active life;
it becomes the frequent seat of many eruptions, all of which denote an
excess of the vital forces. The different kinds of scurf with which
it is covered do not appear elsewhere. In this respect, the skin of
the cranium follows, like the bones of this part and the cerebral
membranes, the early development of the brain, which, on this account
is the seat of diseases in infancy more than at any other age.

The skin of the face seems to be sometimes in less activity. In the
first months after birth, it has not that bright colour which it will
afterwards have upon the cheeks, and which does not commence until the
development of the sinuses and dentition bring to this part more vital
activity for the nutritive work. It is also towards this period that
the eruptions of which this part of the cutaneous system is especially
the seat, like those of the small-pox, measles, &c. begin to take place.

For a long time after birth the skin still preserves a remarkable
degree of softness; a very great quantity of gelatine enters it; this
substance is obtained from it with great ease by ebullition, which,
continued for some time, finally melts this organ entirely. The fibrous
part noticed by Seguin, is in very small quantity. I think it is this
predominance of the gelatinous portion of the skin, which renders that
of young animals easy of digestion. We know that in calves’ heads,
roasted lamb, and small sucking pigs, prepared for our tables, it
presents an aliment which the digestive juices alter with the greatest
ease; whilst that of animals of mature age and especially old ones,
cannot be digested by them. The carnivorous species tear their prey,
feed upon its internal organs, the muscles especially, and leave the
skin. Now what is it that makes the skin of young animals differ from
that of old ones? It is because the gelatinous substance predominates
over the fibrous in the first, and the fibrous predominates in the
second.

The skin of children is gradually thickened; but it is not until the
thirtieth year that it acquires the thickness that it is always to have
afterwards. Till then the different ages are marked in this respect
by different degrees. Take a portion of skin at birth, at two, six,
ten, fifteen, twenty years, &c. you will see these differences in a
remarkable manner. The more its thickness increases the more compact
it becomes; it is because the fibrous substance tends constantly to
predominate over the gelatinous.

As we advance in age, the adhesion of the internal surface of the
dermis with the subjacent cellular texture becomes much greater. It is
more difficult to detach one from the other. On the external surface
the wrinkles of the face are gradually formed. Smiles and tears
agitate the face of the infant the most. One is the expression of the
happiness, the other of the uneasiness which all its passions produce
in its mind. Now the wrinkles which weeping occasions on the eyelids
are marked in rather a more permanent manner, either because weeping
is more frequent than smiling, or because continual winking adds to
the motion which weeping produces, or because less fat is found in
this place. As smiling is on the one hand more rare, and on the other
much fat puffs out the cheeks of the infant, the perpendicular wrinkles
formed by the muscles of the face, which in this motion separate
transversely the features from within outwards, are much slower in
forming. Besides, the nursing of the infant, which requires the
contraction of its face from without inwards, opposes their formation.
The wrinkles of the forehead are always very slow in forming, because
the motions which contract the eyebrow, and those which wrinkle the
forehead, are rare in the infant, who has hardly any of those dark
passions which these motions serve to depict.

The growth of the dermoid system has not remarkable revolutions like
that of most of the others; it goes on in an uniform manner. At the
period of the growth of the hairs, it does not change, because this
growth is absolutely foreign to it, these productions only passing
through it. At puberty it increases in energy like all the other
systems. Until then sweats had not been very copious; for, other things
being equal, we may say that children sweat less in general than
adults, and that the residue of their nutrition passes rather by the
urine, which is probably the reason why they are so remarkably disposed
to calculi. Beyond the twentieth year we begin to sweat more, and until
old age, especially in summer, the fluids appear to go out in this way.


III. _State of the Dermoid System after Growth._

After growth, the skin continues for a long time to have great
activity; the excess of life which animates it, renders it capable of
influencing with ease the other organs if it be but a little excited.
Hence the disposition to pneumonia, pleurisy, &c. from the action of
cold on the skin in sweat, a state in which it is more disposed to
exert an injurious influence upon the internal organs, because its
forces are more excited. As to the different affections which result
from this influence, they depend upon the internal organs upon which it
is directed; so that the same sympathetic irradiations going from the
skin, will produce sometimes an affection of the abdomen, sometimes a
disease of the thorax, according to the age in which the abdominal or
pectoral organs, predominating by their vitality, are more disposed to
answer to the influence directed in general upon the whole economy.

The skin becomes more and more firm and resisting as we advance in age,
as the fibrous substance is constantly tending to a predominance over
the gelatinous. Less blood seems to be carried to it. It becomes less
and less disposed to eruptions, so common in youth and infancy, &c. I
will not speak of its other differences; for all that we have said of
it in the preceding articles relates especially to the adult age.

I will only observe that if, during the greatest part of life, the skin
be so fruitful a source of diseases, and the various alterations it
experiences produce so frequent disorders in the internal organs, it
is only owing to the varied causes of excitement to which it is every
instant subjected. If the glands, the serous surfaces, &c. have an
influence less frequently upon the other organs, it is because being
deeply situated, and almost always in contact with the same excitants,
they are not subject to so many revolutions in their vital forces. The
secreted fluids and those exhaled in the serous and synovial systems
are not, for the same reason, so much subject to those considerable
increases, and those sudden suppressions which so frequently happen to
the sweat.

Observe that society has also multiplied to a great extent the
injurious excitements to which the skin is subjected. These excitements
consist especially in the rapid passage from heat to cold, which
makes the latter act very powerfully upon the cutaneous sensibility,
which like that of all the other systems, answers so much the more
to excitements made upon it, as they are different from those, whose
action they had previously experienced. In the natural state, there
is only the succession of the seasons; nature knows how to connect
insensibly heat with cold, and to make the transition but rarely
abrupt. But in society, the different garments, the artificial degrees
of temperature of our apartments, degrees differing at first from that
of the atmosphere, then varying greatly from each other, so that the
same man who in winter enters thirty apartments, is often subjected to
thirty different temperatures; the hard labour in which most men are
engaged, and which makes them sweat copiously, every thing incessantly
presents numerous causes which make the vital forces of the dermoid
system vary rapidly. Thus the bronchial mucous surface is constantly
in contact in cities, with a thousand excitements that are continually
renewed, and with which the air is not charged in a natural state. Thus
the alimentary substances, continually varying in their composition,
temperature, &c. change the excitement of the gastric mucous surface,
and are the source of many affections, from which most animals are
exempt by the uniformity of their food.

If the skin and the mucous surfaces were always kept at the same
degree of excitement by the constant uniformity of the stimuli, they
would certainly be a much less fruitful source of diseases, as is
clearly proved by the fœtus, which is hardly ever sick, because all the
external causes which act upon its mucous and cutaneous sensibility,
as the heat, the waters of the amnios and the parietes of the womb,
do not vary until birth. At this period, animals brought into a new
medium, find many more varieties in the stimuli which act upon them,
even in a natural state and far from society; thus their diseases are
naturally much more frequent after than before birth. In society, in
which man has increased four, six and even ten times the number of
the stimuli which affect the surfaces destined to be in contact with
the external bodies, is it astonishing that the diseases should be so
disproportioned to those of animals?


IV. _State of the Dermoid System in Old Age._

Towards the decline of life, the dermoid system becomes more and more
firm and compact; it is softened with great difficulty by ebullition.
The gelatine, which it yields, is less abundant and more hard and
consistent. I think it would not be fit to make any kind of glue, even
the strongest, unless mixed with that of adult animals. Its yellowish
tinge becomes very deep. When it is cooled, it requires a much stronger
and more durable fire to melt it; the fibrous portion of the dermis
which does not melt or at least resists for a long time, is infinitely
greater in proportion. It is like the bones in which the gelatinous
portion is in an inverse ratio, and the earthy portion in a direct
ratio to the age.

The dermoid texture becomes then like all the others, dense and stiff;
it is not proper for our food, the teeth cannot tear it. Prepared with
tannin, it is more resisting and less pliable, and cannot on that
account serve for the same purposes as that taken from young animals.
Every one knows the difference of the leather of calves and oxen,
especially when the latter are old. This difference is owing first to
the thickness, which being much greater in the second than the first,
does not allow it to be so easily bent in different directions; and
then to the nature of the texture itself. Cut in two horizontally a
piece of the leather of an ox; each half will be as thin as a piece
of calves skin, and yet it will be less pliable. I do not estimate
here the varieties which may depend on the greater or less quantity of
tannin that may be combined with it; I suppose the proportions to be
all equal.

Submitted to desiccation, the human dermoid texture becomes much more
stiff in old age than in the preceding ones. Maceration softens it with
more difficulty. The hair of a child falls out much sooner by it than
that of an old person; thus it requires longer to clean the skins of
old animals than those of young ones; tanners know this very well. I
would remark upon this subject, that the skins of animals, having more
hairs pass through them, exhibit in comparison with that of man, an
innumerable quantity of little pores on their external surface; which
favours in them on this surface the action of tannin, which insinuating
itself into the dermoid spaces and filling them completely with a new
substance formed by the combination of tannin with gelatine, occupies
entirely the texture of the spaces. The previous maceration to which
the skin has been exposed, favours not only the removal of the hairs,
but facilitates also to a great degree the entrance of the tannin,
by separating the fibres of the spaces, by making them larger, and
increasing the size of the external pores.

The more we advance in age, the less is the quantity of blood that
penetrates the skin. The redness of the cheeks disappears in old
people. We no longer see then the rosy complexion of the young man and
even of the adult, and which arose from the vessels winding through the
cellular texture of the spaces of the chorion.

The continual pressure of external objects increases then remarkably
the adhesion of the subjacent cellular texture to the dermis. They are
separated from each other with great difficulty by carrying the edge
of a scalpel over the internal face of the chorion; a circumstance
which is owing also to this, that the cellular texture having become
more dense, is less easily torn; for this tearing is then necessary,
considering the continuity of the sub-dermoid layer with that which
enters the spaces. The exterior of the skin is uneven and rough. All
the wrinkles of which we have spoken become infinitely more evident;
many belong exclusively to this age.

The vital forces of the dermoid system are more weakened in old age
than those of most of the others, because it is more excited during
life by external bodies. Most of these bodies then make no impression
upon it. The habit of feeling has blunted the animal sensibility. The
touch is exercised but rarely; for, as I have observed, this sense
requires to put it in action, the previous exercise of the will. We
touch, because we have previously seen, heard, tasted, &c. in order
to correct or confirm our other sensations; now the old man, to whom
every thing around is known, to whom nothing is new, is induced to
touch nothing. Compare in this respect the two extreme ages of life.
The infant, to whom every thing that strikes his eyes, his ears, his
nostrils, &c. is unknown, who finds in every thing that surrounds him
new objects of sensation, wishes to touch and lay hold of every thing.
Its little hands are in continual agitation. To touch is a pleasure to
him, for every new object of sensation is agreeable. If in his last
years, man was transported into the midst of objects that never before
struck his senses, he would oftener exercise his touch; but none of
those things excite him among which he has always lived. Hence why old
age is not the age of enjoyments. In fact all our pleasures are almost
relative; we have but little that is absolute; now as habit blunts all
the relative pleasures, which cease because they have existed, the more
the sensations are accumulated by time, the less there are of new ones
left to be experienced, and the more are the sources of happiness dried
up. For a contrary reason, the happiest age is infancy, because it has
before it the whole field of sensations to go over. Man at every step
of his career leaves behind him a cause of his enjoyments. When arrived
at the end he finds only indifference, a state very suitable to his
situation, since it diminishes the distance that separates life from
death.

The organic sensibility of the skin is not less blunted in old age,
than its animal sensibility; hence the following phenomena; 1st,
contagious miasmata are absorbed with difficulty at this age; almost
all pass over the cutaneous surface with impunity. 2d. The exhalation
of sweat is uniformly less; it is hardly ever subject to those great
increases, that are seen in the adult. 3d. The oily fluid is also
furnished in much less quantity; hence the constant dryness of the
exterior of the skin, the cracking of the epidermis in some cases,
&c. 4th. All the diseases which suppose an increase of this organic
sensibility are much more rare. Erysipelas and the different kinds
of eruptions are a proof of it. When these affections take place,
they have a character of remarkable slowness. 5th. The skin resists
external cold much less; it loses easily the caloric of the body,
which always tends to escape in order to be in equilibrium with that
of the surrounding medium; thus old people are always fond of heat.
6th. I am well persuaded that the skin would resist also less, at this
age, a degree of temperature greater than that of the body, and as it
permits the internal caloric to be easily lost in a colder medium, it
would allow the external to penetrate in a warmer one. It would be very
curious to repeat, on the two extreme ages of life, the experiments of
the English physicians.




EPIDERMOID SYSTEM.


If we examine attentively, it is easy to perceive the immense
difference there is between the preceding system and this, which
physiologists have considered as one of its dependancies. Organization,
properties, composition, functions, growth, &c. every thing differs in
the two. By explaining these, the line of demarcation that separates
them will be perceived.

I rank in this system, 1st, the external epidermis; 2d, that which is
spread upon the mucous system, or at least upon one of its parts; 3d,
the nails. Though these last differ very much from the epidermis in
their external appearance, yet they resemble it in so many respects,
that it is difficult not to place them in the same system. In fact the
nails serve as an epidermis for the skin which is subjacent to them;
they are continued with that of the fingers in an evident manner, are
detached and regenerated during life with the same phenomena. The
composition appears to be very analogous. The kind of excrescences is
the same. After death, the nails are detached by the same means as the
epidermis, and then make, as it were, a part of it.


ARTICLE FIRST.

OF THE EXTERNAL EPIDERMIS.

The external epidermis is a transparent membrane, more or less thick,
according to the regions in which it is examined, covering everywhere
the skin, and receiving immediately the excitement of external bodies
which would act too powerfully upon this.


I. _Forms, Relations with the Dermis, &c._

We see upon the epidermis the same wrinkles as upon the skin, because
being exactly contiguous, both wrinkle at the same time. Different
pores open on its surface after having passed through it. Some transmit
the hairs; these are the most apparent; others give passage to the
exhalants. We do not see these in the natural state, because their
course is oblique, and they open between two small layers, which,
being in contact with each other when we do not sweat, conceal their
termination. But if, the skin being very dry, we suddenly sweat, as
after drinking tea, then the little drops which escape from the whole
cutaneous surface, not having had time to run together, but remaining
separate, we see, by the places where they are, the orifice of the
exhalants. Besides, if we examine against the light a considerable
portion of epidermis, its transparency allows us to see many small
pores separated from each other by interstices, and which pass through
it in an oblique direction. It is only in the soles of the feet and the
palms of the hands that we cannot make this observation, which is owing
to the thickness in those parts. It is impossible to distinguish in
these pores the absorbent orifices from those of the exhalants, even
when mercury enters the first by friction.

The internal surface of the epidermis adheres very closely to the skin.
The means of union are at first the exhalants, the absorbents and the
hairs, which in passing through the first, adhere to it more or less,
and thus fix it to the second, from which they arise. By separating
the epidermis by maceration, which is the most proper means, we see on
its internal surface many small elongations of greater or less length,
and which, when examined attentively, appear to be nothing but the
broken extremities of exhalants and absorbents. In fact these little
elongations which are easily raised up, and which then appear like
small ends of thread when they are of some size, but which exhibit only
inequalities when they are left very short, have all of them an oblique
course, and terminate in the pores which, we have said, pass through
the epidermis to go to its surface. Their existence is sufficient, at
the first inspection and without the aid of a microscope, to enable us
to distinguish the internal from the external face of this membrane.
The spaces that separate them are more or less large. About these
spaces, the adhesions are less. It is at this place that the small
epidermoid vesicles are formed with which the skin is covered when
plunged into boiling water. The depressed interstices, which separate
these vesicles, are the places where the exhalants are and which have
prevented the epidermis from being raised up. When ebullition is long
continued, they are detached also.

We cannot doubt then that all these vascular elongations serve
powerfully to unite the epidermis to the chorion. How is the adhesion
formed in their interstices? I know not; but it exists, though it is
less evident. The cellular texture, as I have said, appears to take no
part in it.

Every one knows that many causes destroy the adhesions of the
epidermis, and raise it up. These causes are, 1st, every severe
inflammation, whatever may be its species. We know that after
erysipelas, phlegmon, biles, and cutaneous eruptions of different
natures, the epidermis is always detached; there is then no fluid
that raises it up. The exhalants cannot furnish it, as they are full
of blood; it is dry when detached. 2d. Various cutaneous eruptions,
which have not an inflammatory character, as herpes, &c. also detach
the epidermis at the place where they are. It most commonly comes off
then in the form of dry scales; hence no doubt the idea of some authors
who have attributed to it a scaly structure, which neither observation
nor experiment upon the epidermis in the natural state have proved.
This pealing off in scales is owing to the same cause precisely as the
formation of vesicles which take place the instant after the skin has
been plunged into boiling water, viz. to the greater adhesion of the
exhalant vessels which go to the epidermoid pores. Observe in fact
that it is always in the space between these pores that the scales are
produced, which do not exist in nature, but which arise only from the
manner in which the membrane is raised up. For example, when herpetic
eruptions take place on the chin, the pores through which the hairs
pass are not detached; it is only the epidermis in the space between
these pores; now as these are very near together, these scales are
extremely small; they are almost like dust. 3d. Whenever the epidermis
is raised up by cutaneous inequalities, the least friction detaches it
from these inequalities. Hence why, after strong dry frictions, a rough
skin becomes scaly, whilst a smooth one experiences no alteration; it
is this even, which in the external appearance, contributes much to the
ugliness of the one and the beauty of the other. 4th. After idiopathic
fevers, and even many affections of the internal viscera, the skin
which has felt the sympathetic influence of the disease, becomes the
seat of an alteration which without having any external sign, is
sufficient to break the union of it with the epidermis, which is
everywhere raised up. 5th. We know that the action of a blister, which
draws a large quantity of serum to the external surface of the chorion,
breaks off the exhalants which go from it to the epidermis; so that
this serum is effused under it and forms a more or less considerable
sac. The water does not escape through the open pores, because their
oblique course through the epidermis makes their parietes, when
brought in contact with each other by the pressure of the water,
form an obstacle to it. It is for the same reason, that though these
pores may be very evident, as I have said, in a separate portion of
epidermis when examined against the light, this portion will support
mercury, without giving passage to its particles. 6th. Most of the
preceding means, which produce their effect only by an alteration of
the vital forces, have no effect in raising the epidermis in the dead
body. Putrefaction, maceration and ebullition are those by which it is
effected. All act by breaking the elongations which extend from the
dermis to the epidermis, though the mechanism of this rupture is not
exactly known.


II. _Organization, Composition, &c._

Authors have made many conjectures upon the structure of the epidermis,
which it would be useless to relate here. I shall only speak of what
accurate observation demonstrates. Its thickness is in general very
uniform in all the parts. It has not appeared to me to be increased or
diminished, according to the varieties of thickness of the skin on the
back, the abdomen, the extremities, &c. It is only on the soles of the
feet, the palms of the hands and the corresponding face of the fingers,
that this thickness becomes greater. It is even so great in these
places, that there is no proportion between them and the other parts of
the body as it respects this membrane; it is especially towards the
heel that it exhibits this character. This excessive thickness appears
to be owing to different layers which are applied upon each other, and
which seem to be superadded to the layer of the ordinary epidermis;
but there is also a real difference, though but little known, in the
organization; for example, when the epidermis has been removed from
these parts by maceration, we cannot see, as in the others, those small
appendices or inequalities regularly scattered over it, and which are
the remains of the broken exhalants. In these places these vessels are
torn smoother on the internal surface of the epidermis, on which are
seen only the traces of the wrinkles of which we have spoken.

I attribute to this excessive thickness of the epidermis of the soles
of the feet and the palms of the hands, the difficulty and oftentimes
impossibility of making blisters act in these places, on which I have
often applied them there, because I thought that the sensibility being
greater, they would produce more effect in some diseases. The failure
of my attempts has compelled me to renounce them.

This thickness takes from the epidermis the transparency it has in the
other parts; it is whitish and opake even on the hand and the foot.
Thus the epidermis which, in negroes not being coloured, allows the
blackness of the subjacent reticular texture to be seen, conceals in
part this blackness in these places. I have observed however, by means
of maceration, that the less deep colour of the soles of the feet and
the palms of the hands depends also in this race upon this, that the
reticular texture is really less coloured. We might say that every
thing relates to animal sensibility in this region, the capillary
net-work of which appears to be less, and in which all the phenomena
that are derived from organic sensibility are much less active.

In examining in this relation the hand and foot of a negro, I have
been led to make upon the colour of the reticular body some other
experiments, which form a short digression. 1st. By plunging into
boiling water a piece of the dermis taken from any part it becomes
twice as black, almost immediately; which is probably owing to this,
that the fibres in approximating by the horny hardening, bring
together the colouring particles, whence arises a deeper black. This
phenomenon is very striking, when the piece plunged into the water is
compared with one that has not been. 2d. Maceration for a month or
two, sometimes removes the epidermis without the reticular body, the
seat of colour, and sometimes detaches the whole together. 3d. Being
immersed for some days in cold water produces no sensible effect. 4th.
Long continued stewing hardly changes at all this colour, after the
deep tinge that has been suddenly given to it. Only by scraping with
a scalpel the external surface of the skin which is then reduced to a
kind of gelatinous pulp, we easily detach the coloured reticular body
from it, which however always remains adherent to a small portion of
the chorion. 5th. Sulphuric acid, which reduces the skin like all the
other organs to a kind of pulpy state, also enables us to remove this
coloured portion easily, which is detached in separate pieces, but the
shade of which is hardly altered at all. 6th. Nitric acid, though very
much weakened, does not facilitate so much the removal of this coloured
portion. It yellows the internal surface of the skin and the epidermis;
but it has appeared to me to produce but very little effect upon the
blackness of the reticular body. 7th. A portion of the skin of a negro,
immersed for twenty-four hours in a solution of caustic potash, has
not appeared to me to have undergone any alteration in its colour. I
have made the same observation when I used a weaker solution. 8th.
Putrefaction detaches the coloured portion of the skin, sometimes with
the epidermis, sometimes alone, but it does not alter its colour. I
have not employed other agents to ascertain the nature of this colour
of the skin of negroes. Let us return to the epidermis, which we have
for a moment lost sight of.

Where it is very thick, as on the concave surface of the foot and
the hand, we see that it is evidently formed by layers added to each
other, and which are separated with difficulty, because their adhesion
is so intimate. Everywhere except in the foot and the hand, there is
but a single layer; no fluid penetrates the epidermoid texture. Cut
in different directions either in the living or dead body, it allows
nothing to ooze through it. Their scales are always dry; no blood
vessel exists in them. The absorbents and exhalants only pass through
it without anastomosing, without winding on its interior before opening
on its surface, as happens in the serous membranes, which on this
account become black by injection, though but little blood appears to
enter them during life. The epidermis on the contrary is never coloured
by this means, even when the injection, being very fine and driven
with success, oozes out on the external surface of the skin. Thus, in
inflammation, in which all the cutaneous exhalants are full of blood
which they do not contain in the natural state, this fluid never enters
the epidermis, which is uniformly disconnected with all the diseases
of the subjacent reticular body, and which, being only raised up by
inflammation, is detached and afterwards renewed.

The epidermis has evidently no nerves. It is also destitute of cellular
texture; thus fleshy granulations, which are formed by this texture,
never arise from this membrane; the excrescences of which it is the
seat have not the character of the different tumours which the cellular
texture especially contributes to form, such as fungi, schirri, &c.

From this it is evident that none of the general systems common to all
the organs, enters into the epidermoid system. It has not then the
common base of every organized part; it is as it were inorganic in this
respect.

The epidermoid texture exhibits no fibre in its interior; it has in
general but little resistance, and is broken by a slight distention,
except on the fingers and the hand where it resists more, on account of
its thickness.

The action of the air hardly alters it at all. Only when it is exposed
to it after having been removed in the form of a large layer, it
hardens a little, becomes a little more consistent, and is torn with
less ease. It is of all the organs, next to the hair and the nails,
that which drying changes the least in the natural state. It also
becomes a little more transparent by it; but resumes its ordinary
state when again immersed in water, which proves that it contained a
little of it in this state. The action of the air, which is so quickly
efficacious upon the skin in putrefaction, leaves it then wholly
untouched. It is only raised up, but does not itself putrify. Separated
in this way and washed to cleanse it of the fetid substances that
might adhere to it, it exhales no bad odour. Kept a long time in moist
air, alone and well separated from the neighbouring parts, it does not
alter. It is, next to the hair and the nails, the most incorruptible
of the animal substances. I have preserved a foot found in a cemetery,
the skin and fat of which are transformed into a fat, unctuous and hard
substance, which burns in the candle, whilst the epidermis, which is
very thick, is hardly changed at all in its nature.

The action of water upon the epidermis can be considered under many
relations. 1st. During life it whitens it, when it is some time in
contact with it, and at the same time wrinkles it at different points.
We often see this phenomenon in the hands on coming out of a bath; but
it is particularly evident after ten or twelve hours application of
an emollient cataplasm, in which the action of the farina is nothing,
and in which it is the water that produces the whole effect. This
whiteness of the epidermis appears to be then owing to its having
really imbibed some of the fluid. It is the same phenomenon that
takes place on the serous, fibrous, membranes, &c. which, having
become artificially transparent by drying, whiten again when immersed
in water. Here the epidermis, naturally transparent, whitens by the
addition of this fluid. In this state it renders the sensibility of
the papillæ infinitely more obtuse; I have often made the experiment
upon myself, by applying a cataplasm in the evening and removing it
the next morning. When the water is evaporated which the epidermis has
imbibed, it again becomes transparent, wrinkles, resumes its natural
state, and allows the sensibility of the skin to be again apparent.
This phenomenon is especially observed upon the epidermis of the foot
and the hand, for it is not often as sensible elsewhere. 2d. In the
dead body, the epidermis separated from the skin, and immersed in
water, whitens also, but does not wrinkle. Left to macerate in water,
it does not undergo any putrid alteration. Only there rises on the
surface of the fluid many particles, which being in juxta-position,
form a whitish pellicle of the nature of which I am ignorant. At the
end of two or three months, the epidermis thus left in water, softens,
does not swell, and is torn with great ease; it is not reduced to a
pulp analogous to that of the other organs thus macerated. 3d. When
stewed, the epidermis does not undergo, at the instant of ebullition,
a horny hardening like all the other organs. Hence why, whilst by this
horny hardening the skin is much diminished in extent, the epidermis
which remains the same is obliged to be folded in different directions.
When the ebullition is continued, this membrane becomes less resisting
and breaks with great ease, but is never reduced to gelatine, does
not acquire a yellowish colour, and does not become elastic like the
organs which furnish much of this substance; besides, we know that the
epidermoid texture does not combine with tannin, and that it is even
an obstacle to it when it tends to penetrate the skin. After long
stewing, the different layers which compose the epidermis of the palm
of the hand, and especially that of the sole of the foot, are separated
with great ease; this is the best way of seeing this lamellated
structure. Between these layers there is often formed on the foot small
vesicles filled with serum.

Caloric produces upon the epidermis phenomena wholly different from
those which the other systems experience from the contact of this
substance. A portion of this membrane well dried by the action of
the air, and exposed to the flame of a candle, 1st, does not undergo
hardly at all the horny hardening, as a portion of skin does when thus
treated; 2d, it exhales a fetid odour analogous to that of burnt horn,
and different from that of all the other textures when subjected to
the same experiment; 3d, it burns with great ease, which does not take
place with any of the preceding systems when dried; it is often even
sufficient to put the fire to it at one end to consume it entirely;
4th, at the place of the flame we see a blackish bubbling fluid, from
which often escapes little burning drops, and which is very analogous
to that of a feather when burnt. It is evidently an oil which supports
the combustion by its great abundance, and which does not appear to
be found in as great quantity as in the hair and the nails. This oil
deserves particular examination; it is that which gives out in burning
so disagreeable an odour, and which forms those burning and whitish
drops of which we have spoken. It appears to be of the same nature as
that which Bertholet obtained from the hair in so great a proportion.
After combustion there is left a blackish charcoal, which I have not
analyzed.

Light does not appear to have a great action upon the epidermis, which
I have found of the same colour, in portions of skin blackened by it,
and in those which have been sheltered from it.

Nitric acid yellows very sensibly the epidermis, more even than any
other animal substance; but it does not dissolve it without great
difficulty. The sulphuric on the contrary acts very powerfully upon
it, especially when it is a little concentrated. When it is drawn out
after having been a short time plunged in, it is found to be very
thin, extremely transparent, and almost similar in this respect to the
pellicle that is taken from an onion. This curious phenomenon has often
struck me. When left too long in the acid, the epidermis is finally
entirely dissolved in it.

The alkaline lies dissolve this membrane, but with difficulty. Pure
alkali has a very prompt action upon it.

Alcohol has no influence upon the epidermis.


III. _Properties._

The epidermis has but very little extensibility, since the least
cutaneous tumour can tear it and raise it up in scales, as in herpes,
or in larger pieces, as from a blister. Yet it is not entirely
destitute of it, as the vesicle proves which is formed by this last.
Its contractility of texture is nothing. We observe, that when no
longer distended, this bladder remains flaccid and never contracts.

Every kind of animal sensibility is foreign to the epidermis. We
know that it can be pricked, cut or torn, without being felt. It is
especially on the palms of the hands and the soles of the feet that
these experiments are easily made. The thickness of this membrane is
such in this place, that we can remove layers of it, as we see done by
those who try the edge of an instrument, that it is possible even, as
most cooks do, to put it in contact with live coals, and that it is not
impossible to carry a red hot iron over it. It is by this insensibility
that it blunts the action of the acids, the caustic alkalies, and of
all the powerful stimuli, which when in contact with the dermis laid
bare by a blister, give excessive pain.

The epidermis differs from all the other organs that are destitute,
like it, of animal sensibility, as the cartilages, the tendons, the
aponeuroses, &c. in this, that it is never capable of acquiring it;
whereas the others, if a little excited, often take a degree of it
superior to that of the organs which naturally possess it. Whence does
this arise? From the fact, that in order that the animal sensibility
may arise in an organ it is necessary that the rudiments of it should
be there already, and that this organ should enjoy organic sensibility,
which, when raised by irritation is transformed into animal; now the
epidermis appears to be destitute also of this last property, as well
as of insensible contractility. In fact, 1st, there is no sensible
circulation in it. 2d. The exhalants and absorbents which go through
it, are wholly foreign to it. 3d. No morbid phenomenon, that supposes
organic sensibility, appears in the epidermis. It does not inflame;
it is passive in all cutaneous affections, and never partakes of them
notwithstanding its continuity. The impossibility of inflaming makes
it an obstacle, wherever it exists, to cutaneous adhesions, which
cannot take place until it is removed. Its internal surface, raised by
a blister, and reapplied to the dermis by the evacuation of the serum
of the vesicle by means of a small puncture, never unites again. 4th.
The excrescences of which it is the seat, as corns, some indurations,
&c. are inert and dry like it, and without internal circulation; if
they are painful, it is from the pressure upon the subjacent nerves,
and not from themselves. 5th. No sensible operation is performed in the
epidermis; it is worn incessantly by friction, like inorganic bodies,
and it is afterwards reproduced.

This continual destruction of the epidermis has not sufficiently
arrested the attention of physiologists. The following are the proofs
of its reality; 1st, if with the blade of a knife, we scrape strongly
its external surface, a large quantity of powder is removed which
sulphuric acid easily dissolves, and which is greyish. The epidermis
whitens a little in this place, then resumes its colour, especially if
it is moistened. By scraping again, we do not remove any more powder,
it is necessary in order to obtain it, to wait twelve or twenty hours.
2d. This substance becomes superabundant, when the skin has not been
washed for a long time. Hence why those who soak their feet that have
not been cleaned for a long time, detach so great a quantity of it. It
is especially on the sole of the foot that this substance is formed
in abundance. We often observe in dead bodies that it forms almost a
layer in addition to the epidermis, but which is very distinct from
it, and can be removed with ease. I attribute this circumstance to the
thickness which the epidermis has in this place. We should no doubt
find as much upon the hand, were it not for the continual friction
of this part. We see it often on the patients in hospitals, after
remaining a long time in bed without having been cleansed.

Water naturally removes this substance, that is produced by the
destruction of the epidermis, and, which, mixing with the residue of
transpiration, that the air cannot carry off by evaporation, renders
bathing, as I have observed, a natural want. Though it may be neither
exhaled nor absorbed, and though its production may appear to be
owing to mechanical friction, yet we can, in its relation, consider
the epidermis as an emunctory of the body, since it is renewed by a
substance coming from the dermis, as fast as it is removed.

It is evident, as the epidermis has no vital properties, that it cannot
be the seat of any kind of sympathies, which are aberrations of these
properties. Hence its life is extremely obscure, I doubt even if it
possesses vitality. We might almost say that it is a semi-organized
body, inorganic even, which nature has placed between external
inanimate bodies and the dermis, which is completely organized, in
order to assist their passage and guard against their force.

The epidermis has a property very distinct from those of most of the
other systems; it is that of being reproduced when it has been removed.
It grows anew and is formed again with an appearance exactly similar to
what it first exhibited; it is that which makes it differ from all the
other systems, as the cellular, which throw out vegetations when they
are laid bare, but which are only reproduced in an irregular manner,
and wholly different from their natural state. How is the epidermis
thus reproduced? Is it the pressure of the atmospheric air which
renders the external surface of the skin callous? Is it the air, which,
by combining with the products which escape from this surface, forms a
new compound? I know not. What is certain is, 1st, that this production
is wholly different from that of the internal organs; 2d, that it
cannot take place except upon the skin, and that the fine pellicle
that covers all the other cicatrized parts, after a wound with loss
of substance, does not resemble it at all and presents even a texture
wholly different. Thus this pellicle is not raised up by the different
means which raise the epidermis; thus it often becomes the seat of
acute sensibility which is never the case with the epidermis. This is
what takes place especially in changes of weather, a time in which the
cicatrices become, as we know, very painful; I have often observed,
that not only the interior, but the pellicle even of the cicatrix are
then sensible. Besides, when this pellicle is formed, red blood vessels
evidently penetrate it, whilst nothing similar is observed in the
formation of the epidermis.

It is this faculty of reproduction which is put in action in many
epidermoid excrescences, as in corns, and callosities which have
nothing in common but the name with those which form the edge of
fistulas, &c. All these excrescences are insensible, without vessels or
nerves, of the same consistence and the same colour as the epidermis;
they are often removed from it and afterwards formed again. It appears
that external pressure has much influence upon their development; too
narrow shoes and the solid bodies which are used on the hands of smiths
and other workmen are the frequent cause of them.

I preserved a great part of the skin of a man who died at the Hôtel
Dieu, and his epidermis, which was treble the thickness from his birth
and even in the womb of his mother, that it is in the ordinary state,
had been subject during his life to a continual desquamation which
made the whole of it appear as if covered with herpes, though nothing
similar to this affection existed upon the dermis, which was perfectly
sound. The face alone was exempt from this defect of conformation.

The epidermis is not only reproduced when the whole of it has been
removed, but also when the superficial layers alone have been taken
away, especially on the foot and the hand on which other layers arise
upon those which the cutting has laid bare; which proves that they are
not, as has been said, the juices of the reticular body which form it
by drying.


IV. _Development._

Those who have thought that the epidermis is formed by pressure, would
be convinced that this is not the case if they would examine that of
the fœtus, which is very distinct, more even in proportion than many
other systems. We observe it when the skin begins to leave the pulpy
state of which we have spoken. At the end of the fifth month, it has
proportions analogous to those which it will afterwards exhibit. It is
very thick on the soles of the feet and the palms of the hands, and
very thin elsewhere; it is easily detached by all the means we have
pointed out. We know that in a fœtus that has died and become putrid
in the womb, it is found in great measure detached. At the place of the
umbilical cord, it is continued in an insensible manner with the skin.

At birth, though it is in contact with a fluid that is new to it, it
does not undergo a great alteration; which proves that the air has
little or no agency in its formation. It becomes thicker as we advance
in age, and follows, in this respect, nearly the same proportions as
the skin. Beyond the twenty-sixth or thirtieth year it increases no
more. I have often raised up in many places the epidermis of an old
person; it has not appeared to me to differ much from that of the
adult; it is a little more subject to scale off and it is a little
thicker. In some miserable objects which come to hospitals, there is
often vermin in cracks of the epidermis, whose layers are afterwards
separated by them and in which they live; so that I have seen the
epidermis in this way conceal thousands of little animals, which were
evidently found between the layers of this membrane, and which were not
upon the reticular body and the papillæ. It is the only means that has
shown to me the lamellated structure of the epidermis, in any other
place than on the foot and the hand, in which I have never seen vermin.

The cracks of the epidermis in old age appear to arise from its dryness
owing to the want of exhalation; it is that which renders the skin so
rough and harsh. What contributes to it also is, that as it has many
inequalities on account of its numerous folds, frictions being more
felt in these prominent places, make the epidermis scale off; thus in
the adult the same cause renders it scaly on a tubercular skin, whilst
a skin that is smooth and well distended with fat, undergoes every kind
of friction without desquamation.


ARTICLE SECOND.

INTERNAL EPIDERMIS.

All authors have admitted the epidermis of the mucous membranes.
It appears that most have believed that it is only this portion
of the skin which descends into the cavities to line them. Haller
in particular is of this opinion. But the slightest inspection is
sufficient to show, that here as upon the skin, it forms only a
superficial layer over the papillary body and the chorion. Boiling
water which detaches it from the palate, the tongue and the pharynx
even, enables us to see the two other layers.


I. _Epidermis of the origin of the Mucous Surfaces._

The epidermis is very distinct upon all the origins of the mucous
system, upon the glans, the entrance of the anus, the urethra, the
nasal fossæ, the mouth, &c. It is demonstrated in these places by
the excoriations that take place there, upon the lips especially, by
dissection with a very fine lancet, by the action of boiling water,
maceration, putrefaction and even epispastics, as is proved by the fact
that the ancients employed this method to make the edges of a hare-lip
raw. The delicacy of this epidermis is much greater than on the skin;
and as it is more in the interior this delicacy increases. It is to
this circumstance that must be attributed the ease with which different
remarkable modifications are produced through this membrane, when in
galvanic processes, we arm with zinc the surface of the tongue and with
another metal the mucous surface of the conjunctiva, the pituitary
membrane, the surface of the rectum, the gums, &c. and bring in mediate
or immediate contact these different metals.

The mucous epidermis is quickly reproduced when it has been removed.
Destitute of every kind of animal and organic sensibility, it is in
this respect, destined like the skin, to defend the very sensitive
papillary body that is subjacent to it. It is to its presence upon the
mucous membranes, that should be in part attributed the faculty they
have of being exposed to the air, and even to the contact of external
bodies, without exfoliating or inflaming as in preternatural anus,
prolapsus of the rectum, &c. whilst the serous membranes cannot bear
this contact with impunity.

Besides, the nature of the mucous epidermis is the same as that of
the cutaneous. Submitted to the action of the same agents, it gives
the same results. The excrescences formed on its surface are also
analogous, though much more rare. It becomes callous by pressure.
Chopart relates the case of a shepherd, whose urethra became so, from
frequently introducing a small stick to procure pleasure. We know the
density that this covering has in the stomach of the gallinaceous
animals, and in certain cases in which the mucous membranes come out
of the body as in prolapsus of the rectum, the vagina, the womb, &c.
Sometimes in those cases the pressure of the clothes produces in this
epidermis a thickness evidently greater than what is natural to it; it
is this which then makes these membranes lose in part the bright red
that characterizes them in the interior.


II. _Epidermis of the deep seated mucous surfaces._

The epidermis gradually becomes more delicate, and is soon almost
insensible, on the internal mucous membranes. 1st. In the stomach, the
intestines, the bladder, the gall-bladder, the vesiculæ seminales, in
all the excretories, &c. the most delicate instrument cannot raise
it up. 2d. In the maceration and ebullition of the mucous system of
these parts, I have never seen the epidermis raised up on its surface.
3d. I have drawn out of the abdomen of a dog a portion of intestine;
its mucous coat has been laid bare by an incision, and I have applied
an epispastic to it; more redness was seen upon the free surface of
this coat, but no pellicle was raised up from it. 4th. We do not see
in preternatural anuses, complicated with inversion, excoriations
analogous to those of which the surface of the lips, that of the glans,
&c. are the seat. 5th. I have already had frequent occasion to open
bodies affected with acute or chronic catarrhs of the intestines,
the stomach, the bladder, &c. now I have never seen the epidermis
separated by inflammation, as happens after erysipelas, phlegmon, &c.
upon the cutaneous organ. 6th. We do not see upon the deep seated
mucous surfaces those exfoliations, desquamations, &c. so frequent upon
this after many affections.

From all these considerations it would appear, that the epidermis does
not exist upon the deep seated mucous surfaces, and the great quantity
of mucous juices constantly poured out by the subjacent glands,
supplies its place in defending the papillæ and the chorion from the
impression of substances heterogeneous to the economy, contained in
the internal cavities. Yet there is a circumstance that would seem to
demonstrate the existence of the epidermis upon the deep seated mucous
surfaces; it is the separation of preternatural membranes, which are
often detached from these surfaces, and which may be considered as a
kind of epidermoid exfoliation. Many authors give examples of these
membranes formed either upon the bladder and voided by the urethra,
or upon the stomach and œsophagus and thrown up by vomiting, or upon
the intestines and expelled with the alvine evacuations; Haller has
collected many cases. Dr. Montaigu informed me that he saw a membrane
vomited up, which formed a sac without a rent, exactly analogous to
that of the stomach whose internal surface it lined. Desault saw a sac
almost analogous to the bladder, voided by a patient who was affected
with retention of urine.

I confess that I have made no observation on this point, so that I
cannot say what is the nature of these membranes. But authors in
general agree in attributing to them a soft and pulpy nature, which
does not appear to me to accord with that of the epidermis. I have
many times seen at the Hôtel Dieu white membranes detached from the
œsophagus after poisoning with the nitric acid. But these membranes
are evidently the superficial portion of the mucous organ, which is
disorganized, and thrown off by suppuration which takes place below. It
is thus that cutaneous eschars fall off in the form of membranes from
large burns; in this way the osseous layers are formed in necrosis,
which are only the superficies of the bone that dies and is detached in
a lamellated form.

From this, the existence of the epidermis of the deep seated mucous
surfaces appears to me to be very uncertain, and cannot be admitted
till a new examination, which will, I think, prove rather against
than in favour of its existence. What is the place in which the
epidermis terminates that lines the origin of the mucous surfaces,
or if it exists everywhere, where does it begin to become no longer
apparent from the action of our different reagents? We cannot, I think,
determine with precision; it diminishes in an insensible manner, and is
lost as it were by degrees.


ARTICLE THIRD.

OF THE NAILS.

All the fingers have at their extremity, on the outer side or that of
extension, hard, transparent and elastic layers, of the nature of the
horns of many animals, and which are called nails.


I. _Forms, Extent, Relations, &c._

The nails of man differ from those of most other animals, in their
breadth and want of thickness. The first makes them better adapted to
support the extremity of the fingers, which is broader than in most
animals for the perfection of touch; the second renders them less fit
to serve for defence or as a means of aggression.

Most people cut their nails even with their fingers, so that the length
of these bodies which is seen is not what is natural to them. When
allowed to grow, they lengthen and turn over on the side of flexion,
and cover entirely the lower end of the fingers. This growth has a
certain limit which the nail cannot pass, and which it attains when it
exhibits at its extremity a cutting and sharp edge. As long as this
edge has the appearance of having a part cut off, the nail continues to
grow.

We usually think that the habit of cutting our nails is a thing of
mere decorum. But if we reflect a little upon society and the numerous
arts to which it gives rise, upon the perfection, delicacy, precision
and rapidity of the motions which the fingers are often forced to
execute, upon the necessity of approximating them, crossing them in
a thousand different ways, &c. we shall soon see that this habit is
almost inevitably the result of the social state, and what appears to
us the effect of fashion is that of necessity. The sense of touch in
man in a natural state is coarse and obscure; it is only necessary that
he should seize objects destined for his nourishment, his defence, his
aggressions, &c. that he should climb especially and attach himself to
trees to keep himself upon them; now his nails are for this purpose
of great use. What he loses in this respect in society, he seems to
gain by the precision and extent which are added to his touch, and
by the faculty which the fingers acquire of distinguishing the most
delicate tangible qualities. In the first state, his hands are of great
assistance to him in locomotion. In the second, they contribute hardly
at all to this use, and they gain in the partial motions of their
fingers what they lose in their motions as a whole, which become of
less urgent necessity.

The nail has three distinct parts in the natural state; one posterior,
concealed on both sides by the integuments; another middle, free only
on one side, and the third anterior, without adhesion at either side.

The posterior portion of the nail is nearly a sixth part of its extent.
Its convex surface adheres very intimately to the epidermis, which
goes in the following manner to fix it. After having covered over the
portion of the finger corresponding with flexion, it is reflected
upon the concave edge where the skin terminates and where the nail
begins to become external; it commonly forms all around this edge a
kind of small string that is very distinct and has a small groove in
the top of it, and which is evidently composed entirely of epidermis,
since we can cut the whole of it without giving any pain, and which is
afterwards easily reproduced. After having formed this string, which
is in the form of a parabola, the epidermis is again reflected, passes
between the skin and the nail, and is glued, if we may so say, to the
concave surface of the latter, without being intermixed with it; for
we can remove it with ease by scraping with a scalpel. So that the
dermis which covers the superior portion is really between two layers
of epidermis. After having thus fixed the nail, and having arrived at
its posterior edge, the epidermis is continued and identified as it
were with this edge, whose evident delicacy and softness approximate it
in nature to this membranous layer. Hence it follows that without the
adhesion of the epidermis to the nail, there would be between them, a
kind of cul-de-sac. Some authors have thought that the extensor tendon
is extended as far; but it is easy to see that it does not go beyond
the tubercle which terminates behind the phalanx. The nail does not
reach this tubercle, there is a space of three lines between them. The
concave surface of the posterior portion of the nail corresponds with
the same substance as the middle portion.

This middle portion is bare on its convex surface, which is smooth,
whitish behind where this colour forms a kind of half moon, reddish in
the greater part of its extent, a colour which is foreign to it and
which it derives from the subjacent texture. Upon the sides, the skin
covers this surface a little, and terminates afterwards by continuing
the concave and free edge of which we have spoken. The epidermis forms
also in this place a small string which is continued on each side with
that pointed out above; then it unites to the nail and adheres to its
lateral edges with which it is identified. The concave surface of
this middle portion is fixed in front by the epidermis, which, after
having covered the extremity of the fingers, and having arrived at the
place where the nail ceases to be free, is separated from the dermis,
and adheres to the whole length of the nail in a curved line; then by
mixing with it, it seems to form its internal lamina. The dermis on the
contrary is continued on the convexity of the last phalanx, has there a
remarkable consistence, a reddish appearance, and a texture like pulp
and wholly different from what is observed elsewhere; more vessels run
through it; there is no distinct space in it, and no elongation goes
from it to the surface of the nail of which the epidermis forms a part.
We do not see on this surface, as on those of the other parts of the
epidermis, those threads, which are the remains of the broken exhalants
and of which we have spoken; thus the sweat never passes through the
nail. There is neither any oily oozing upon its surface; whence it
follows that water is not formed into little drops on the exterior of
its horny laminæ. Hence the nail is evidently insulated from all the
other organs except the epidermis, with which it is continued on its
concave face and especially on its posterior and lateral edges. Thus
observe that when collections of pus or other affections have broken
this continuity behind or on the sides, the whole of the nail, though
unaffected in the middle falls off.

The free or anterior portion of the nail is of a length which it is
difficult to determine. I have never seen it allowed to take its
natural growth. I have only observed that if it is permitted to grow to
a considerable size, we see evidently that it has a greater thickness
than the posterior and middle portion. In general, the thickness,
resistance and hardness of the nail increase in a gradual manner from
the posterior to the anterior part; we shall now examine to what this
is owing.


II. _Organization; Properties, &c._

In order to observe the organization of the nails advantageously, it is
necessary to take those that are very distinct, as those of the great
toe, the thumb, &c. We then see evidently that a single lamina occupies
the whole of their convex surface. Behind, this lamina exists alone;
hence the extreme thickness of the nails at this place. But as we
examine towards the front, we see new laminæ successively added to it,
on the concave surface; so that the nail becomes successively thicker.
These laminæ can be easily raised up layer by layer. The most anterior
are the shortest. They often exhibit upon the concave surface of the
nail an infinite number of very evident small striæ, all longitudinal
and parallel, and which make us attribute to it a fibrous texture. At
other times this arrangement is less evident.

What is the nature of the laminæ which form the nails? I believe that
they are almost precisely the same as the epidermis. What proves it
is, 1st, that the most superficial is evidently continued with it by
its edges; there is no intermediate agent between them. 2d. I have
already observed that the nails are detached, and then regenerated
exactly like the epidermis. They have two modes of increase; one in
length, when we cut their extremities; the other in thickness, when we
detach only a lamina, which is soon formed again. When the whole of the
nail comes off, all the portion of the dermis which covers the back of
the last phalanx, contributes at the same time to form it anew by its
external surface. 3d. There is the same obscurity in the vitality of
the nails as in that of the epidermis. No trace of animal sensibility
is discoverable in them. The excruciating pain that is experienced
when they are pulled out arises solely from the sensibility of the
subjacent pulpy texture; it is from the same cause as in pulling out
the hair. There is no organic sensibility, no internal circulation and
consequently no heat inherent in the texture of the nails; thus the
horns of animals are nearly of the same degree of temperature as the
atmosphere, whilst some external productions with evident vital forces,
though raised up like horns, have a temperature equal to that of the
body. Such are the combs of the cock of our country, and those which
are more striking of the cock-turkey. Compare these excrescences with
those on the feet of these animals, which are horny, and the difference
of temperature is evident. 4th. The nails give out when burning a
disagreeable odour, analogous to that of the epidermis under the same
circumstances; they exhibit then the same phenomena. Their combustion
is supported, like that of the epidermis, by an oil of which they
contain a great quantity. 5th. If maceration and stewing do not produce
upon the nails that want of consistence, that kind of brittleness,
if I may so express myself, which they produce upon the epidermis, it
appears to be owing only to their greater solidity. 6th. The action of
the nitric, sulphuric acids, &c. has exhibited to me nearly the same
phenomena as upon the epidermis.

Every thing then appears to establish the most exact analogy in
the composition, organization and properties of the nails and the
epidermis. There is no doubt a difference of principles between them,
since the appearance is not the same, and since, though many epidermoid
layers may be in juxta position as on the soles of the feet and the
palms of the hands, they do not exhibit the form and texture of the
nails; so that we cannot consider these as mere layers of epidermis
applied to each other. Chemists must ascertain what these differences
are, which are certainly very slight. Thus nature often employs
indifferently the two organs for the same uses; it is thus that on the
sole of the foot of man and many analogous species, there is a thick
epidermis; whilst on the feet of animals with hoofs, we see a horny
substance of the nature of the human nail.

An evident proof of the slight degree of internal motion which is
going on in the epidermis and the nails, of the kind of inertia in
which they are in relation to the constant motion of composition and
decomposition, which constitutes nutrition, and of the insensibility
which they exhibit to various excitants, is the ease with which they
are penetrated by different colouring substances, and the very long
time they retain them. We know this effect with regard to the nails
of dyers. Many savage people who paint the face, various parts of the
body, and often even the whole of the external surface of the body,
preserve for a long time, without a new coat, the colour which they
have artificially given themselves. I have removed the epidermis of
a portion of skin of the arm of a dead body, which was coloured blue
during life; this colour was not only on the surface of the membrane,
but penetrated the whole of it, like a piece of cloth that had been
soaked in it. Yet the pores were as evident as before, and the sweat
could pass through them; I presume this secretion goes on as usual in
savages who paint the skin. Thus the cloth which is immersed in a dye,
has not its pores closed by it. I may make use of this comparison, as
the epidermis and the nails are really species of inorganic bodies. Lay
any organ bare and paint it in this way; the colour, together with the
contact of the air will irritate and inflame it, and the suppuration
arising from this inflammation will soon throw out the colouring
particles, which nutrition would have done, if inflammation had not.
There is a means however which can perpetuate the colour, even upon
organs, which, very sensible like the skin, are constantly subject to
the double nutritive motion; it is that of using the colours with a red
hot iron. It is in this way I am convinced that the letters or coloured
figures which most soldiers mark upon themselves, with a red hot pin,
have their seat not only in the epidermis, but also in the chorion
itself.


_Development._

The nails have in the fœtus a very considerable consistence, whilst
the skin is still pulpy; but their tenuity is then extreme. But they
thicken and acquire greater consistence as the fœtus increases in
size. They have not at birth a length proportionable to what they are
afterwards to have. They do not extend beyond the ends of the fingers
which are often much the longest; so that it is not till after birth
that they are bent over and exceed the fingers in length, for both of
these would be useless in the womb of the mother, as there is nothing
there for the fœtus to seize upon. Their transparency allows us
evidently to see, at the moment of birth, first the black colour of the
blood which before circulated in the arteries, and then the vermilion
colour which respiration suddenly imparts to it. As we advance in age,
the nails grow in the same proportions as the epidermis, but they have
nothing peculiar in their growth. In old people they become extremely
thick.

These organs experience during life those diseases only which
are analogous to those of the epidermis. These are excrescences,
augmentations of size, &c. and other productions, the texture of
which is precisely the same as that of the nail, and in which there
is neither more sensibility, nor more circulation, nor more heat, nor
more life; a remarkable character which distinguishes them from those
tumours which arise upon the other organs with very active vitality, as
upon the skin, the muscles, &c. tumours the texture of which is very
different from that of the organs which have produced them, and which
most usually have properties entirely different. But the epidermoid
excrescences are in every respect analogous to the epidermis.




PILOUS SYSTEM.


The adjective by which I characterize this system, is derived from the
latin substantive which signifies the organs of which it is composed.
Hair is found less generally upon man than upon most other animals.
It forms upon them a kind of covering external to the skin, which,
lessening in part the contact of external bodies, makes the cutaneous
animal sensibility perform a less important part, and establishes
less numerous relations between these bodies and them. External life
is then, in this respect, more limited in them than in man, in whom a
delicate epidermis and a few hairs thinly scattered over it, separate
the organ of feeling from surrounding objects, the least impression of
which is felt, and which, owing to this, keep the animal sensibility
in permanent activity; thus man is designed to live more without than
within himself. The pleasures of reproduction and digestion constitute
exclusively the happiness of animals. That of man is in part the
result of them; but an order of pleasures wholly different, purely
intellectual and in relation only with external sensations, enlarges
immensely by its presence, and contracts by its absence, the field of
this happiness.

The hair of man covers especially the cranium, some parts of the face,
the front of the trunk, the genital organs, the extremities, &c. The
quantity varies remarkably, as well as the form, length, &c. In order
to form an accurate idea of it, we shall now consider it separately in
the different organs, we shall then treat of its general organization,
properties and development.


ARTICLE FIRST.

EXAMINATION OF THE PILOUS SYSTEM IN THE DIFFERENT REGIONS.

This system must be considered on the head, the trunk and the
extremities.


I. _Pilous System of the Head._

The head is the part of the body in which this system predominates;
it covers the whole cranium and defends it against the impression of
external bodies, as the hairy coat of quadrupeds defends them. Thus
this part is the least capable of exercising the sense of touch, either
from the obscurity of the animal sensibility arising from this hairy
covering, or because its convex form allows it to be in contact with
external bodies only by a small surface.

The face is less generally covered with hairs, though many are found
upon it, especially in men. This part, in which in a very small space
are collected the greatest number of our means of communication with
external objects, viz. the organs of taste, smell, sight and even
hearing, has but very little to do with the sense of touch, on account
of its villous arrangement. Its form is also badly adapted to this
sense. The mouth which is flattened cannot be applied to external
bodies. Thus whilst the snout which is elongated in most quadrupeds,
performs the double function of first feeling all bodies, turning them
in various directions in order to ascertain their tangible qualities,
and then of seizing them for nourishment, the mouth of man serves only
for this last use; it is the hands which are destined for the first.
Thus observe that all animals, even the most of those with clavicles,
almost uniformly direct their snout towards the earth, whilst the mouth
of man is naturally destined to an opposite position.


_Of the Hairs of the Head._

They occupy upon the cranium all the space which corresponds with
the occipital, parietal, the squamous portion of the temporal and a
small portion of the frontal bones. Their limits do not vary on the
sides; they always correspond above the ear. Behind, they sometimes
go down upon the superior part of the neck; at others, they do not
extend beyond the head. In applying blisters on the ligamentum nuchæ,
we observe in this respect, almost as many varieties as there are
subjects. We know how variable these limits are in front. Sometimes
extended lower down, sometimes carried higher up, sometimes describing
a curved line, and at others forming a real triangle the anterior point
of which corresponds with the median line, they have really nothing
constant.

These inequalities alone determine the breadth or narrowness of the
forehead, whilst its degrees of inclination depend solely upon the bone
which forms it. It is in this way that the hair contributes a little
to the expression of the face; I say a little, for it is less to the
breadth of the forehead than to its approximation to a perpendicular,
that we attach the ideas of majesty and greatness which characterize
heroes and gods. The poets, as we know, have particularly celebrated
the forehead of the god of thunder. Observe in relation to this subject
that there is a great difference between that which expresses majesty
or abjectness in the face, from that which serves there to express the
passions. It is the osseous structure of this region and the degree
of inclination resulting from this structure, which serve for the
first use, and it is especially the muscular motions which contribute
to the second. Why? Because majesty, grandeur, &c. are especially
connected with the extent of the understanding, and the understanding
has its seat in the brain, and because the various capacities of the
cranium, which contain this organ, and which correspond with its
various degrees of development, have inevitably an influence upon the
different dimensions of the face. Now as the bony structure is a thing
constant and invariable, the air of majesty or abjectness remains
always imprinted upon the face. On the contrary, the passions which
especially affect the epigastric organs, which afterwards excite the
facial muscles, have necessarily a transitory expression.

The number of hairs is very variable on the same surface. In some
people they are very close together and even all touch; in others more
thinly scattered, they allow in part the skin of the cranium to be seen
in their interstices, a circumstance which is either owing to original
conformation, or to a disease which makes them fall out in part. They
have, like the nails, a determinate growth which they do not exceed.
We know but little of the limit of this growth. Yet we have seen them
reach to the waist, the thighs, and the legs even. It appears that
in women they have a greater growth; we might say, that nature has
compensated this sex in this way for the want of hair in many other
parts. Floating upon the shoulders, the breast, the trunk, &c. they
form in the natural state a sort of protection from the injuries of
the air and the light. Their extent evidently proves that man was
destined to an erect attitude. In fact, in the attitude of quadrupeds,
they would trail much upon the earth, and form an obstacle to motion.
The hair of no animal, I believe, in a natural attitude retards his
progress so much, as the hair of man then would.

Man, who opposes nature in every thing, has made it a habit in most
societies to cut the hair, the beard, &c. By common people, it is
considered merely a thing of fashion; by the physician, as a practice
which has perhaps a greater influence than is thought upon the
functions. In fact, in the natural state when the pilous system has
once acquired its growth, it no longer exhibits the constant motion
of composition and decomposition. On the contrary, in man who cuts
it, it is constantly the seat of this motion and of that of growth.
This practice perpetuates then the phenomena which take place in them
in infancy, and consequently keeps up there a more active work, which
perhaps is performed at the expense of that of many other parts.

The natural difference of the hair has much influence upon its length;
that which is smooth and curls but little is in general the longest.
The more it has the opposite characters, the shorter it is, as is
proved by that of negroes and those white people whose hair curls like
theirs.

The tenuity of the hair is very great, yet its resistance is in
proportion very considerable. There is no part in the economy, not
even those of the fibrous system, which can support so great a weight
in proportion to its size. Thus woven strings of hair would have an
enormous resistance, if they were sufficiently long to be employed for
different uses.

The colour of the hair varies remarkably according to country,
latitude, climate, temperature, &c. This colour is even, like that
of the skin, a characteristic attribute of the different human races.
Naturalists have been much occupied with this subject, and I refer to
their works.

In our climate the principal colours are black, flaxen and bright red.
They are, as it were, the three general types to which may be referred
many particular shades. The black has under it the brown, the chesnut,
&c. The flaxen is connected on the one hand with the bright red and on
the other with the chesnut. The bright red which touches the flaxen by
one of its extreme shades, goes by an opposite shade to the natural
colour of certain flames.

All physicians have considered the colour of the hair as among the
characters of the temperaments. Black indicates strength and vigour.
The figure of a wrestler with flaxen hair would be almost ridiculous.
This colour is the attribute of weakness and delicacy; it floats upon
the head of figures which painters have made strangers to the great
passions, to powerful and heroic deeds; it is found upon the figures
of young people, in pictures where laughter, sport, grace and pleasure
preside over the subjects. These two colours, black and flaxen, as
well as their secondary shades, are found distributed among women in
nearly equal proportion; now reflect upon the kind of sentiment this
sex inspires according to the colour of the hair, without regard to
any other consideration, and you will see that a woman with flaxen
hair creates a sentiment which beauty and weakness united seem to
dictate. The epithets that we employ express this double attribute. On
the contrary, the term brunette announces in her that it designates,
a mixture of force and beauty. Beauty is then a common gift which
attracts us, but which, differently modified by external forms,
attracts us by touching, interesting and exciting us. Eyes in which
langour is depicted, are frequently associated with flaxen hair; whilst
black hair is almost always met with, in those whose vivacity and
sparkling seem to proclaim an excess of life which seeks to be diffused.

Habit which accustoms us to every thing, changes our taste in regard
to the colour of the hair, as it does to that of our dress. Black,
flaxen and their numerous shades are in turns fashionable in France;
and as the organization does not change with our taste, we have
contrived artificial hair; a happy means, which seems to subject to our
inconstancy the invariable course of nature, and which, changing at our
will the expression which the physiognomy borrows from the hair, can at
every instant exhibit man under forms which fashion extols to day, and
which ridicule pursues tomorrow. Now among these numberless variations
which succeed each other among us in the fashion of the hair, bright
red and its various shades never find a place. Most people have a
decided aversion to it. It is almost, in our eyes, a mal-formation to
be born with it. This opinion is too general not to have some real
foundation. The principle appears to me to be the usual connexion
between the hair and the temperament and of course the character which
results from this; now the kind of character connected with this kind
of hair is not commonly the happiest, though there are many exceptions
to this principle, which is proverbial. Another reason for the aversion
to hair of a bright red, is that the oily fluid which lubricates it
often exhales a fetid odour foreign to the other kinds of hair.

What is the relation that can exist between the hair and the character?
Has the first an influence upon the second? No; the following is the
way in which it should be considered. Every man has his peculiar kind
of organization and constitution. This forms the temperament; now, to
each kind is attached on the one hand this or that species of hair, and
on the other the predominance of some internal viscera, which though
less apparent is not less real. This predominance disposes evidently
to certain passions, which are the principal attributes of character;
then the colour of the hair and character are two different results
from the same cause, viz. constitution; but one has no influence upon
the other.

The hair coming out of the cutaneous pores has such a direction, that
that of the anterior part of the cranium is almost always oblique
in front, and tends to fall over the forehead; that of the middle
and posterior part pierces the skin perpendicularly, and that of the
posterior and inferior part traverses it obliquely, so as to fall
naturally down the length of the posterior part of the neck. It is the
same with that of the sides, which its direction as well as its weight,
carries upon the region of the ear which it covers.


_Eyebrows._

Upon the arch which borders the orbit above, is found a collection of
hairs forming a portion of a circle more or less evident, which shades
the eye and defends it from the too powerful impression of the rays of
light. The hairs of the eyebrows are thicker together in persons of
dark complexion, than in those of light. More numerous within, they
sometimes unite together the two eyebrows upon the nasal prominence,
and thus shade the root of the nose. Fewer without, they there cause
the eyebrow to terminate in a point. All are obliquely directed
from within outwards. Sometimes towards the internal side, they go
perpendicularly forwards. Their length is scarcely more than half an
inch; they do not exceed this except in some extraordinary cases. Their
colour is usually, though not invariably, the same as that of the hair.
They are firmer, more resisting and larger than the hairs of the head.
If they were longer they would curl like the hairs on the genital
parts, of the nature of which they partake.

The eyebrows enjoy two evident motions. 1st. They are depressed and
carried inwards, by forming over the eye a very evident arch. 2d. They
are raised up and separated from each other, by expanding the parts
around the orbit. The length between the extremes of these two motions
is nearly an inch. The first motion takes place to defend the eye
from a very bright light. It expresses also the melancholy and gloomy
passions; hence the reason no doubt why the same word is applied to
the moral state of the mind, and to the row of hairs of which we are
treating. Observe on this subject that the sanguineous and choleric
temperaments, which are the most disposed to the passions which make
the eyebrows contract, are precisely those in which the hairs that
compose them are found in general the most evident. The second motion
enables us to receive upon the region of the orbit a great quantity
of the rays of light; it allows us to raise the upper eyelid to a
great extent in order to open the eye wide, which the first evidently
prevents. It expresses also the gay passions, those which dilate the
face. Painters have studied more than anatomists, the different degrees
of elevation and depression of the eyebrows.


_Eyelashes._

Upon both eyelids there exists a small row of hairs, a little longer
than those of the eyebrows, of the same nature as them, directed
obliquely forwards, crossing each other when the two eyelids are
brought together, and serving to defend the eye from the small
particles floating in the air. In general they do not curl; when they
do and turn towards the eye, an irritation ensues, and they must be cut
off. Sometimes a bad direction is the cause of this irritation.

I would remark on the subject of the eyelashes, that all the openings
of communication with the interior, as those of the meatus auditorius
externus, the nose and the anus, and oftentimes also the orifices of
the lactiferous tubes, are surrounded with a great number of hairs
which defend these openings from external bodies. Around the mouth the
beard takes the place of these hairs; the urethra has none, but the
prepuce at its orifice is instead of them.


_Beard._

The males of most animals are distinguished from the females by some
external productions. The comb of the cock, the mane of the lion, the
horns of the stag, &c. are examples of these distinctive characters.
In man, the beard is the principal attribute of the male. It occupies
all the chin, the sides of the face, both lips and the superior part
of the neck. It leaves the cheeks bare as well as the parts around the
eyes; thus observe that it is there that the passions are principally
depicted, the expression of which would be concealed by the hairs, if
the lower part of the face was the seat of them.

The beard, not so long in general as the hair of the head, is longer
than that of every other part of the body. It is very commonly of the
colour of the first, though more rarely flaxen and is more frequently
of a bright red, which it often is in persons with flaxen hair. The
nature of the hairs of the beard is the same as that of the hairs of
the genital parts, the eyebrows, &c. They curl, are stiffer, more
resisting and uniformly less oily than the hair of the head.

The quantity of beard varies remarkably in different men. Those in whom
it is abundant and of a deep black are in general strong and vigorous.
Observe also that the strongest males in the different species of
animals are those, in whom the external production which distinguishes
them from the females, is the most conspicuous. We might say that this
characteristic production is the index of the strength or weakness of
their constitution. A small lion has not a noble mane; great horns
belong to a well made stag, and long, twisted ones to a good formed
ram. Observe that it is not the same with the other hairs common to
the two sexes. Often in a weak man, those of the arms, the thighs, &c.
are as evident and even more numerous, than in the most muscular.

The habit of cutting the beard as most Europeans do, of preserving
it like the Asiatics and of dressing it in different ways like the
Chinese, gives a different expression to the face which characterizes
the people. A masculine, vigorous physiogomy which expresses strength
and energy, cannot be deprived of this external attribute without
losing a part of its character. That of the Orientals exhibits an
appearance which coincides with the strength of their bodies, and
forms a contrast with the effeminacy of their manners. I do not know
if, in consulting the history of the different people who allow their
beard to grow, and that of nations who cut it, we might not be tempted
to believe that muscular force is to a certain extent connected with
its existence, and that this force is always diminished a little when
we are constantly deprived of it. Every one knows the vigour of the
ancients, that of the people with long beards, and that even of certain
men who, among us, allow their beards to grow in conformity with the
laws of monkish institutions. No doubt many causes may make weakness
exist with a beard; but in a general view I think we can admit that
there is a certain relation between it and strength. Take from a cock
his comb, which is the characteristic of the male, as the beard is that
of man, and he will lose strength. I am persuaded that we might take
from the lion a part of his power by taking away his mane. We know
the result of the experiments of Russel upon the castration of stags;
their horns, after this operation have grown in an irregular manner,
or have not even grown at all. This external attribute of the male in
this species, appears as we know at the period of virility, when the
vital forces are increased. It is the same with the human beard. This
coincidence would alone prove that the use of this last is to serve
for an external character to the male sex. The eunuch, whose powers are
feeble, loses also oftentimes much of his beard.

Such are our prejudices in regard to the idea we form of beauty, that
we ridicule what is really and absolutely so, for that is certainly
so which indicates organic perfection. A peacock without his tail of
emeralds, a ram or a stag without their horns, displease us; why does
not man without his beard?


II. _Of the Pilous System of the Trunk._

The hairs on the trunk are very variable. Some men appear as it were
shaggy, whilst others are almost without hairs. There are more of them
generally on the anterior than on the posterior part of the trunk. It
is principally along the linea alba and upon the chest, that they are
found in man. This last part is in general destitute of them in woman,
who has usually very few on the trunk.

Both sexes have a very considerable quantity on the genital parts. They
are there, as I have said, of the nature of the beard. Less frequently
flaxen than the hair of the head, as frequently of a bright red, they
are most usually black. They are, next to the beard, the longest hairs.
They have generally no determinate direction; each hair almost has a
different one. Few animals, like man, exhibit this excess of hair upon
the genital parts. There is a great difference in individuals as to its
quantity. The blackness and abundance coincide in general with strength.


III. _Pilous System of the Extremities._

Man has many hairs upon the whole surface of his extremities. The
proportion of number is nearly the same in all; but the length varies
very much; in some, they form only a down; in others, they are a little
longer; whilst in others, they are nearly of an inch in length, reach
over each other, and give the extremities a shaggy appearance.

At the top of the superior extremities, there is in the hollow of the
axilla a collection of hairs which are longer than the others, and are
nearly of the nature of those of the genital parts. Nothing similar is
seen on the inferior extremities.

The pilous system does not exist on the internal part of the arm and
fore-arm in many men, in whom we see it only behind and on the sides.
It is more uniform on the inferior extremities. The back of the foot
and hand always have hairs. They are never seen on the sole of the one
or the palm of the other; a circumstance of essential advantage to the
perfection of touch.


ARTICLE SECOND.

ORGANIZATION OF THE PILOUS SYSTEM.

Whatever varieties exist in the form, size and arrangement of the
hairs, their organization is nearly the same in all. We shall now
examine this organization in a general manner. Chirac, Malpighi and all
anatomists since them, have explained very well in some respects, and
very badly in others, the structure of the hairs of the head, which is
nearly the same as that of all the other hairs. The following is what
careful dissection has shown me concerning it.


I. _Origin of the Hairs._

The hairs of the head, and in general all the hairs, arise from a
sub-cutaneous fat, or the cellular texture of the parts which are
destitute of this fluid. Each is contained at its origin, in a kind
of small membranous canal, the nature of which is perfectly unknown
to me, and whose transparent parietes allow the hair to be plainly
seen, when we have separated them with a delicate scalpel from the
surrounding parts. This small cylindrical canal accompanies the hair to
the corresponding pore of the skin, insinuates itself into this pore,
passes through it, extends to the epidermis and is intermixed there
with the texture of this membrane, but goes no further. The length of
this canal, and consequently of the course which the hair runs under
and in the skin, is nearly five lines in the hairs of the head. There
is no adhesion between the hair and the internal surface of this small
canal, except at the enlarged base of the first where, it receives its
nourishment. Thus, by opening the canal at this place, and destroying
its adhesions there, the hair becomes free, and is drawn from without
inwards with great ease, by taking hold of its enlarged end with small
forceps. In this way, the canal is insulated. I have thus dissected and
separated, upon a surface of two inches, a very great number of these
canals which appear, when nothing but them is left on the internal
surface of the skin, like so many small elongations of it.

Are there vessels and nerves in this small cylindrical sac which
contains the origin of the hairs? We see distinctly elongations going
to its external surface, especially towards its extremity opposite
to the skin; but dissection does not teach us the nature of these
elongations. I have never been able to trace them to a neighbouring
vessel or nerve. Haller has not been more successful, though he speaks
of authors who have traced nerves to the origin of the hairs. I presume
however that these elongations are especially vascular. Is there a
fluid between the origin of the hair and its covering? By opening
the latter, nothing escapes, though some authors have pretended the
contrary. Besides, if this fluid is in the form of dew, as upon the
serous surfaces, it cannot be distinguished.

It is in the middle of this small cylindrical sac, of which I have just
spoken, that the origin of the hair is found. We see at its extremity
an enlargement oftentimes almost insensible, at others very evident,
though always less than has been said. This enlargement is of the same
colour and nature as the hair itself. It adheres to the canal very
probably by the vessels and perhaps the nerves it receives from it. The
hair which arises from it goes through its canal without adhering, as I
have said, to its parietes, passes with it through the oblique pore of
the dermis, leaves it at the epidermis, and goes outward.

All authors say that the hair does not pierce the epidermis, but only
raises it up, and that this forms a sheath which accompanies it to its
extremity. This assertion is incorrect; in fact, 1st, the hair is as
thick in its canal of origin as it is out of it. 2d. This canal being
opened at its extremity opposite to the skin, we can draw out of it,
as I have said, the whole hair with great ease, and without the least
resistance; which would not be the case however if the covering of the
epidermis was to be broken. It appears that from the enlargement of
its extremity, the hair has no adhesion either in the sub-cutaneous
canal, or in its passage through the skin, or the epidermis. 3d. If the
cutaneous epidermis was raised up to cover the hair, this would have a
treble thickness, unless this epidermis became wonderfully thin upon
it. 4th. We do not see this pretended rising up by drawing out a hair
of the head; on the contrary a depression exists at the place where
this comes out. The cutaneous epidermis furnishes nothing then to the
hairs, though the nature of them may be in part the same as its own,
and it is proper to consider them as uniform in their structure from
one extremity to the other.

Under the skin, through it and out of it, the hair is composed of two
distinct parts. One external, forms a canal which extends from the
enlargement of the dermoid extremity to the opposite one; the other
internal, which composes as it were the medulla of it, is of an unknown
nature.


II. _External Covering of the Hairs._

The external covering of the hair appears to be of the nature of the
epidermis. It has in fact almost all the attributes of it. 1st. The
hairs of the head burn exactly like this membrane, give out when
burning an analogous odour, and leave after combustion a similar kind
of coal; now it is principally to the external portion that these
phenomena are owing. 2d. Water penetrates the hairs with great ease;
hence very useful hygrometers can be constructed with them; now the
same is true of the epidermis; and moistened hairs in foggy weather
present in this respect a phenomenon analogous to that of the epidermis
softened, wrinkled and whitened by the contact of a cataplasm. 3d. It
is by means of the epidermoid covering that the hairs are foreign to
life, that they are insensible and never become the seat of any acute
or chronic affection. 4th. This covering is white, whatever may be the
colour of the hairs. The cause of the colour resides in the internal
medulla; thus the epidermis of negroes and that of white people differ
but very little. Hence why when the internal substance of the hair has
disappeared, the canal remaining alone exhibits a more or less evident
whiteness. 5th. In this state, though the interior of the hair may be
dead, the epidermoid exterior, which is independent of it, preserves
most commonly the faculty of growing when it is cut; thus the cutaneous
epidermis is truly foreign to all the subjacent diseases of the skin.
6th. I presume that it is this covering which gives to the hairs of the
head the property of remaining so long uninjured. When removed far from
the access of the air, they remain unaltered for ages; they have not
in them the principle of decomposition of the other animal substances.
They never become putrid either in air or water. Thus we have seen that
the cutaneous epidermis never undergoes putrefaction, which seizes upon
the subjacent parts.

It appears however that the hairs are more unalterable than the
epidermis, and that there is even a difference of nature between them.
In fact, 1st, maceration and ebullition, which make the epidermis very
easy to be broken, though they soften it but little, leave the hairs
with their usual resistance, unless carried to degrees that I have not
tried. By boiling and macerating them comparatively with the epidermis,
we easily make this observation. 2d. The acids act less efficaciously
upon the hairs than upon this membrane; but the alkalies dissolve them
with as much and even more ease. 3d. A thread of epidermis of equal
thickness would be incomparably less resisting than a hair. 4th. The
hairs can, like the epidermis, be painted of different colours; but
they do not retain them so long, and on this account the colour must be
renewed oftener.

Some modern authors have said that there is detached from the external
covering of the hairs a kind of scales which form as it were little
branches to them. We do not see these elongations. However the
experiment mentioned by Fourcroy, and which consists in this, that by
rubbing a hair between the fingers, it is raised like the heads of
some species of grain in the direction from its base to its point, this
experiment, I say, appears to prove the existence of these insensible
elongations, which perform also an essential part in the adhesion of
the hairs of the head to each other, an adhesion that is such that when
they have remained a long time without being separated, as in long
diseases, it is only done with the greatest difficulty.

Sometimes the hairs are bifurcated in a very evident manner at their
extremity.

It is the greater or less thickness of the epidermoid covering of
the hairs, which constitutes the different nature of them. Thick
and compact on the genital parts, the chin, &c. it is less easily
penetrated with water, and renders the hairs more elastic there and
more capable of curling. Loose and thin in the hairs of the head, it
makes them more smooth, and gives them more sensibly the property of
the hygrometer. It is the peculiar nature of this external covering,
which gives to the hairs of the head and the hair of negroes the
character which distinguishes them.

From what we have just said it is evident that the external covering of
the hairs of the head is the part of them which is essentially inert
and foreign to life. It is not the same with their internal substance.


III. _Internal Substance of the Hairs._

This substance is the most important; it is this which essentially
characterizes the hairs, which I should have ranked in the epidermoid
system, if they had nothing but their external covering, as is the case
when they become white.

We are entirely ignorant of the nature of this internal substance. It
can only be presumed that there are extremely delicate vessels inclosed
in the common epidermoid covering containing a colouring substance,
which stagnates in these vessels, or at least is subjected in them to
a very slow nutritive motion. Among these vessels, do any of them as
on the skin, open outwards to throw off fluids? Many physiologists
have thought so, and on this account they have considered the hairs as
real emunctories. I do not believe that we have any anatomical data
upon this point; but the plica polonica, a singular disease in which
the hair when cut pours out blood, evidently proves that they have
exhalants in a natural state, which then becoming enlarged and dilated,
pour out a fluid that they before refused to admit. Besides, there is
no doubt that the pilous exhalants, infinitely less active than the
cutaneous, are a much less copious emunctory. As to the absorptions
which some have pretended are made by the vessels of the hairs, I think
that nothing can prove them.

From what we have just said upon the internal substance of the hairs,
it appears that it has a true analogy with the reticular body of the
skin, and that, like it, it arises from two sorts of vessels, one in
which the colouring matter stagnates, the other which gives passage, in
some cases at least, to fluids, and in which there is consequently a
kind of circulation.

The colouring substance of the hairs has some analogy with that of
the skin. Thus we observe that the first, like the second, is blacker
in warm climates and nearer the equator than in colder ones; thus
red hair is frequently found with freckles which are more or less
abundantly spread upon the skin of some people, and which are evidently
seated in the reticular body, as I have ascertained in many patients
who had these marks, and in whom the epidermis was raised up either
by erysipelas or a blister. The acids however change the colour of
the hair more than they do that of the skin of negroes. The muriatic
whitens at first the hairs of the head which become yellow in drying;
the nitric yellows, and the sulphuric leaves them black.

That which especially interests us in the internal substance of the
hairs, is the real vitality which it enjoys, and which essentially
distinguishes it from the external covering. It is to this character
that must be referred the following phenomena.

1st. The different passions of the mind have a remarkable influence
upon the internal substance of the hairs. Often, in a very short time,
grief has changed the colour of it, and whitened it by occasioning no
doubt the reabsorption of the fluid contained in the small capillary
vessels. Many authors have related facts of this kind. Some, even
Haller, have doubted them. But I know at least five or six instances
in which a discoloration has taken place in less than eight days. The
hair of a person of my acquaintance became almost entirely white in
the course of a night upon the receipt of melancholy intelligence. In
these changes, the epidermoid covering remains the same, preserves its
texture, its nature and its properties; the internal substance only
is altered. It is said that terror can make the hair stand an end;
painters express it even by this external attribute; I know not to what
extent we should give belief to this phenomenon which I have never
seen; but it is an opinion too generally received not to have some real
foundation. Now if fear acts so powerfully upon the hair, if it can
give it a real motion, is it astonishing that grief and pain should
suddenly change the fluids that are found in it, and deprive it even of
these fluids?

2d. The plica polonica, of which I spoke just now, in which the hairs
of the head become, when they are cut or even when they are not, the
seat of a bloody exhalation, and in which they have a remarkable excess
of life, evidently resides in the internal substance; the epidermoid
covering has no connexion with it. Some authors even say that this
internal substance acquires sometimes a fleshy nature; then their
covering is raised up in scales.

3d. We know the danger of cutting the hair after many acute diseases. I
have already seen a melancholy instance of it. Many physicians, Lanoix
in particular, have related others. Now, to what are these accidents
owing? It is certainly not to the contact of the air, from which the
hair defends the head; for these accidents take place, though the head
may be covered. It can only be owing to this, that the growth of the
hairs that are cut, calls to these organs a vital activity which the
internal viscera soon sympathetically feel; hence the pains of the
head, the affections of the eyes, &c. observed in these cases. It is
a species of active sympathy exerted by the hair upon the viscera;
now, every organ which sympathizes has a real vitality, and enjoys
very distinct vital properties. The epidermis never takes part in
sympathies, because it is almost completely inert, is hardly organized,
is not at the level of the other organs, and cannot consequently
correspond with them. The danger of cutting the hair after severe
sickness, gives me opportunity to observe that it is often as dangerous
to remove suddenly the vermin from the heads of children during these
diseases. I have seen three or four instances of accidents from this
cause.

4th. The hairs not only influence other systems, but are also
influenced by them. This is what we often see after acute diseases,
in which the roots sympathetically affected, repel the fluids that
come to nourish them, die, and the hairs fall out. Observe that this
falling out of the hair very rarely takes place at the same time with
the desquamation of the epidermis; which proves, that the generally
admitted opinion of the origin of the external covering of the hairs is
entirely false, and that, though very analogous to the epidermis, this
covering does not arise from it, as I have said.

5th. Many animals lose at one season of the year their hairy covering,
which is afterwards reproduced; now the period of its regeneration
is often that of many diseases, and almost always that of a greater
weakness than at other times. We might say that the nutritive work
which then calls to the exterior much vital force, diminishes this
force in the other regions. Man is not subject to these annual renewals
of the external productions which cover his body, like birds, many
quadrupeds, reptiles, &c. It is a cause of less diseases. In fact,
a thousand different causes would no doubt have frequently deranged
these renewals in society, as a thousand causes disturb the menstrual
evacuation, &c. hence the various diseases we escape by the want of
this renewal. Man is in general subjected to fewer causes of natural
revolutions, than most animals.

6th. Heat and cold have also oftentimes an influence upon the internal
substance of the hairs. We know that in some animals, as rabbits,
hares, &c. they become white in the winter and resume their original
colour in the summer.

7th. A short time after painting the hairs of the head black, a fashion
now more common in France than at the period in which they powdered
them, there is often experienced pains in the head and a swelling of
the hairy scalp, though the skin has been in no way concerned, has not
been pulled, and the hair only has been affected.

It follows from all we have just said, that the hairs analogous, by
their external covering, to the epidermis; foreign by means of it,
if we may so say, to life, belong to it much more particularly by
their internal substance, a substance whose nature is yet but little
known, as I have already said. What moreover evidently proves this
assertion, is that the phenomena of which I have just spoken, and to
which I could add many others, cease to be evident in persons, in
whom the hairs having become white, have no longer any thing but the
epidermoid covering, the internal substance having in part disappeared;
particular observation proves this. It may be however that in this case
that portion alone of this internal substance, corresponding to the
colour, is destroyed, whilst that which is the seat of the exhalations
continues to live as usual; and, in this respect, white hairs may
experience vital phenomena, of which, I believe, there are a few
examples. But all this is subordinate to the future experiments, which
will elucidate the pilous structure more than it now is.


ARTICLE THIRD.

PROPERTIES OF THE PILOUS SYSTEM.

The hairs experience but a slight degree of the horny hardening when
exposed to the action of caloric. They then turn in various directions,
curl and twist; but this arises from a cause entirely different from
that of the horny hardening of the other organs. The caloric then
removes the moisture with which the hairs are constantly penetrated,
and thus approximates their particles. Thus when the hair is moistened
by fog, a bath, &c. the curls disappear. The oily substances that
are used at the toilet, give a coat that is insoluble in water, and
preserve the curling, by preventing it from penetrating the hairs. Some
time after the head has been washed, they curl more, as we have had
occasion to observe since the Grecian head dresses have been in fashion
among us. This at first appears to be contradictory, but it is not
so. In fact by then rubbing the hairs much, the unctuous substance is
removed, which always surrounds them, or this substance combines with
the soap, if the water contains it, as is often the case; by this means
it easily penetrates the hairs, the pores of which remain open, and by
afterwards evaporating with the fluids that were already there, and
which the unctuous substance retained, it leaves these organs more dry
than they were, and consequently more disposed to curl.

A proof, that it is the epidermoid covering which thus imbibes the
moisture that it afterwards loses in the state which succeeds the
curling, is, that the detached epidermis can be curled with a hot iron,
and afterwards rendered supple by soaking it in water.

The contractility and extensibility of texture are very indistinct in
the hairs; it is their resistance which prevents their rupture; they
can hardly be stretched at all.

They have no animal sensibility when pulled; the pain that arises from
it has its seat especially in the skin through which they pass. Thus
when drawn opposite to their direction, we suffer much more than by
stretching them in the direction of their pores. I do not deny however
that these elongations, which fix their origin to the neighbouring
parts, may be also the seat of pain when the hairs are pulled. These
organs have no animal contractility.

The organic properties certainly exist in their internal substance.
The changes which this substance undergoes can only depend on the
different alterations which affect these properties. The organic
sensibility and the insensible contractility especially are raised in
it in a remarkable degree in the plica polonica; now in order to have
the degree of energy which they then do, they must have existed there
in a natural state. It is these two properties, that, the sympathies of
which we have spoken, put into action. The organic contractility is
nothing in the hairs.

Yet we cannot deny that in the natural state, these organs are, next
to the epidermis and the nails, those in which life is the least
active, those which have the least numerous relations with the other
organs. Whilst every thing is destroyed in most of the other systems by
diseases, this is most often unaffected by them; it grows as usual, and
appears to be in no wise disturbed; it has then a manner of being, of
existing, wholly different from the others.

In general, the external productions of animals, as the feathers, the
hair, the scales, &c. seem to form a separate class of organs, foreign
to the life of the internal organs; it is almost like the different
species of mosses that grow upon trees, without making essentially a
part of them.


ARTICLE FOURTH.

DEVELOPMENT OF THE PILOUS SYSTEM.


I. _State of this System in the First Age._

In the first months of the fœtus there are no hairs on the skin which
is then gelatinous. It is when the fibres of the dermoid texture are
formed, that there begins to appear on the head a light down, an
indication of the hairs which are afterwards to arise. This down is
whitish and concealed by that fatty and unctuous substance, which we
have said is deposited on the external surface of the skin at this age.
Soon this down, which appears to be but the external covering of the
hairs, which is then of extreme tenuity, begins to be coloured black
or flaxen, according to the tint that is afterwards to predominate;
it is the internal substance that forms it. The colour remains faint
until after birth. At this period the hairs are often more than half an
inch long. Upon all the rest of the body there is only the down, the
precursor of the hairs; the face especially has much of it. The hairs
of the head are then in advance at one period of the other hairs, in
their growth.

After birth the hairs grow much more rapidly than before. It is
precisely the reverse of most of the other parts, whose growth is
more rapid in the womb of the mother. During the whole of youth this
system has a tint less deep, than it is afterwards to have. The flaxen
becomes nearer the chesnut, and this nearer black, and the first tints
of the bright red grow many degrees darker towards the period from
the twenty-sixth to the thirtieth year. The light tints are to the
pilous system in youth, what the imperfectly developed forms are to
the muscular, cellular, &c. Oftentimes that which is to be afterwards
flaxen, approaches a whitish tint, which is owing only to the nature
of the internal substance, and not to its absence in old age. Thus the
white of the Albinos depends also upon the peculiar species of this
internal substance. Many hairs are wanting upon the body of the young
man.


II. _State of the Pilous System in the following Ages._

At puberty there is a remarkable revolution in this system which
becomes almost double. The hairs of the genital parts are formed; the
beard which is, as I have said, the characteristic attribute of the
male in the human species, is also then developed. We might say that
there was the same relation between the hairs of the neighbourhood
of the testicles and those of the beard, as between the testicles
themselves and the organs of the voice, between the womb and the mammæ.
The beard is, in this respect, the external sign of virility. Some time
before it comes out, we see under the skin the sac which contains the
origin of the hairs; it is already very evidently formed, and permits
the principle of the organ to be seen which it is to contain, as I have
oftentimes ascertained; thus the sac of the tooth exists a long time
before the tooth is cut.

At the same time the hairs of the axilla grow also; those of the trunk
and extremities, which were then almost in a state of down, become
larger, assume a determinate colour, and increase even much in number.

Why does puberty occasion this general growth in the pilous system?
This is asking the reason of all the other phenomena which appear at
this period. I would only observe that the hairs of the head, the
eyebrows, the eyelashes and the hairs at the openings of the body, are
those which are the least affected by this revolution. Besides, this
growth is gradual; it requires at least two or three years for the
beard to become what it is always to be.

In the following ages the hairs undergo but few changes; they grow in
proportion as they are cut in different parts, and are the seat of a
constant external work; now, observe that this work is more prompt, and
the growth of the hairs consequently more rapid, in summer in which the
cutaneous organ is especially in action, than in winter in which it is
contracted; an additional proof of the real vitality of the organic
forces of the internal substance of the hairs.


III. _State of the Pilous System in Old Age._

Towards the end of life, the pilous system is affected by the general
obliteration which takes place in almost all the external vessels;
it ceases at first to receive the colouring substance. The internal
substance dies, the epidermoid covering remains alone; the hairs become
white. The hairs of the head appear the first, and are the first to
die. The beard, the hairs of the genital parts and then those of all
the parts of the body afterwards die. Besides, there is a great variety
among men as it respects the period in which the hairs whiten; in some,
this phenomenon begins about the thirtieth year, and even sooner, in
others it is towards the fortieth, fiftieth or sixtieth. A thousand
causes arising from the passions of the mind, from diseases, aliments,
&c. can have an influence in society upon this premature death, so
common in many men, but which does not take place in animals, who are
not exposed from their kind of life, to the same revolutions, until the
last years.

The hairs, after remaining white for a longer or shorter time, finally
fall out; then the sac which covered the origin of them flattens down
and entirely disappears. I have examined many bald heads; the skin of
the cranium was perfectly smooth on its internal surface, though it
had been separated from the cellular texture. No trace is discoverable
there of the innumerable appendices which the canals form, after the
hairs they contain have been drawn inwards. I have also dissected a man
who after a putrid fever had become almost entirely bald. There were
all these little canals entire, and in the bottom of them could already
be seen the rudiments of new hairs. There is then this difference
between the falling out of the hairs of old people, and that which
is the consequence of diseases, that every thing dies in the first,
because the vessels which go to the root cease to transmit fluids to
it; whereas in the second case the hair alone falls out, and its sac
remains.

It is a pretty generally received opinion that the hair, the nails and
the epidermis continue to grow after death. We have, I think, but few
data respecting this singular phenomenon. I am however certain that I
observed a real elongation of the hairs of a chin of a head that had
been carefully shaved, and which I macerated eight days in a cellar.
An attendant of the dissecting room, who prepares many heads for
the bones, informed me that he had often made the same remark, when
putrefaction is prevented for some time. What is certain also is, that
the growth of the beard is not in the direct ratio of the vital forces;
in the diseases which affect these forces with a general prostration,
it grows as much as in those in which there is a general exaltation
of these forces. We remark this in hospitals where at the side of an
inflammatory fever, there is often found a putrid or slow nervous
one. Besides, why should there not be sufficient tonic forces left in
the hairs to grow some time after general death, as there is in the
lymphatics to absorb, &c.?

The different phenomena which the hair, the epidermis, the skin, and
in general all the external organs experience in the successive ages,
are wholly owing, like those of the internal organs, to the laws of
nutrition, and not to the action of surrounding bodies. This is an
essential difference between organic and inorganic bodies. The latter
are gradually altered in two ways by the contact of external bodies
which act upon them, 1st, mechanically by friction, tearing, &c. &c.
2d, chemically, by combining with them, as for example, the air whose
different principles undergo many combinations which change its nature
and that of the bodies with which it is in contact. In this respect
all inorganic bodies grow old. At the end of some time, they have no
longer the exterior which characterized them in the beginning. Observe
monuments, pictures, engravings, earths, metals, stones, &c. &c. every
thing which in the arts, commerce, sciences, in the uses of life or
in the phenomena of nature is formed of any inert bodies, whether
these bodies have never lived, or having lived, have not been able to
preserve themselves after death, as the solid portions of vegetables,
the bones, the horns, the hair of animals, &c. every thing finally has
the indelible stamp of time; every thing grows old; every thing loses
its freshness, every thing changes on the exterior of inert, as well
as on that of organic bodies; but as in the first surrounding bodies
alone have acted, the internal part is still young, whilst the external
is old, if I may be allowed to use two very improper words. Thus the
rock whose surface is blackened by the lapse of years, is the same in
the interior as when it was created. On the contrary in animals and
vegetables, the internal organs are worn out, as well as the exterior.
Time is marked upon the viscera, as well as upon the forehead of the
aged. Surrounding bodies act upon us, wear out life, if we may so say;
but it is as stimuli that they exert their action; it is by exhausting
the sensibility and contractility, and not by combination, mechanical
contact or friction. Language ought to express this difference. We do
not use the term _young_ when viewing the exterior of a new building,
a new garment, or a picture recently painted; why do we say an _old_
monument, an _old_ piece of cloth, &c.? if it is a metaphor, very well;
but this word cannot express a state analogous in its nature, to that
of an old animal, an old plant, &c.


IV. _Preternatural Development._

There are three principal cases in which the hairs are preternaturally
developed in the economy.

1st. Sometimes they are formed on the internal surface of the mucous
membranes; they have been seen in the bladder, the stomach and the
intestines; many authors have given cases of them. I have found them
upon the calculi of the kidney. I have seen in the gall-bladder at one
time a dozen of nearly an inch in length, and which were evidently
implanted in its surface.

2d. There is often seen on the skin preternatural collections of
them, which are usually a defect from birth. These collections are
particularly observed upon some of those productions or irregular
excrescences, that are called nævi materni. There was exhibited at
Paris, six years since, an unfortunate person, who had from his birth
his face covered with hairs almost like those of a wild boar; and to
whom there came on at the age of thirty-six years, that particular
species of elephantiasis, in which the skin of the face increased in
size, exhibits, if we may so say, the features of the lion, a species
which I have since had occasion to observe upon a natural skin. This
double circumstance gave to the face of this man an air of ferocity
which it is impossible to describe. Many of the stories circulated by
the vulgar concerning men with the heads of wild boars, bears, &c. are
nothing but these nævi in the face, with a growth of hair upon them.

3d. Hairs are often preternaturally developed in cysts, in those of the
ovaria especially. A great many instances have been related. Haller in
particular has collected many; I have seen two. The following is what
they exhibit; a considerable large sac contained many very distinct
small balls, analogous to those of the dung of sheep, formed by a
fat, unctuous, whitish substance, very different in its appearance
from ordinary fat. On the internal surface of this sac were implanted
many hairs, which the least force could remove, because they hardly
penetrated below the surface. These hairs were black. Many already
detached were found crossed in different directions, in the small balls
of fatty matter, which was like spermaceti; for it very much resembled
the substance into which the fat is changed by maceration.


END OF THE LAST VOLUME.




ANALYTICAL TABLE OF CONTENTS.


VOLUME FIRST.
                                                                   PAGE.

  Preface by the Translator.                                           5

  Preface by the Author.                                           _ib._


 GENERAL OBSERVATIONS.

 Of Animate and Inanimate Beings.—Of their Laws.—Of the Sciences which
 treat of their Phenomena.                                             9


 I. _General Remarks upon the Physiological and Physical Sciences._

 The differences between these sciences are derived from the properties
 which preside over the phenomena.—The necessity of always connecting
 the second with the first.—Periods at which this progress commenced in
 the physical sciences. False applications made to the physiological
 sciences.—The necessity of following in these the same course as in
 the others.                                                           9


 II. _Of the Vital Properties, and their influence upon the phenomena
 of the Physiological and Physical Sciences._

 Vital properties considered in the series of living beings.—Of those
 which animate plants.—Consequences in regard to their diseases.—Of
 those which belong to animals.—Consequences in regard to their
 diseases.—Examination of each vital property under the relation
 of the diseases over which it presides.—Necessity of referring to
 these properties the action of medicines.—Uncertainty of the Materia
 Medica.—Each vital property has a particular class of medicines which
 act upon it.—Proofs.—Inconveniences of describing morbid phenomena
 and those of medicines in too general a manner.—Consequences of the
 preceding remarks.                                                   13



 III. _Characters of the Vital Properties, compared with the characters
 of the Physical Properties._

 Extreme variableness of the first, invariableness of the
 second.—Consequences of this principle as it regards the
 phenomena.—There can only be diseases where there are vital
 properties.—Why.—The progress of the physiological and physical
 sciences wholly different in this respect.—Differences between
 animate and inanimate solids and fluids.—The vital properties become
 exhausted, the physical do not.—Consequences.—The latter are inherent
 in matter, the others are not.—General remarks upon the enumeration
 of the differences of animate and inanimate bodies.—Particular remark
 relative to sympathies.—Their general phenomena.                     23


 IV. _Of the Vital Properties and their Phenomena considered in
 relation to the Solids and the Fluids._

 Division of the fluids into those of composition and those of
 decomposition.—The vital properties are seated essentially in the
 solids.—These are the seat of almost all the morbid symptoms.—The
 fluids however may be affected.—Different attributes of the fluids
 of composition and of those of decomposition in diseases.—How the
 alterations of the first may take place.—Of those of the second.—Of
 the cases in which the solids and the fluids are primarily
 affected.—Division of diseases in this view.—The question must
 necessarily be considered in many points of view.—What is true on
 one side is not so on another.—Of the vitality of the fluids.—What
 it is.—Their alterations affect their vitality.—New proofs of these
 alterations.—How the fluids are assimilated and altered.             29


 V. _Of the Properties Independent of Life._

 Properties of texture.—Of contractility by the horny hardening.—Of
 the agents which put it into action.—It is of two kinds.—Characters
 of each.—Their differences.—Almost all the solids undergo the horny
 hardening.—Condition which it requires.—Of the horny hardening during
 life and after death.—Difference of this contractility from the
 others.—General remarks.                                             38




 VI. _General Observations upon the Organization of Animals._

 Of the simple systems.—Necessity of considering them
 abstractedly.—Their difference of forms.—Their variety of
 organization, 1st, in the peculiar texture; 2d, in the common
 parts.—Manner of knowing these differences.—Differences of the
 vital properties and of texture.—Of the peculiar life.—It cannot be
 understood of the compound organs, but of the simple systems.—Examples
 which prove this assertion in the different organs.                  44


 VII. _Consequences of the preceding Principles relative to Diseases._

 Each texture can be separately affected in an organ.—This even almost
 always happens.—Various proofs of this assertion.—Observations upon
 different diseases.—Sympathies do not take place in an organ as a
 whole, but in some one texture of this organ.—Why.—Of sympathetic
 fevers.—The different inflammations vary in each texture.—Phenomena
 of the different kinds of virus variable from the same cause.—Yet
 the different textures of the same organ have a certain dependance
 upon each other.—Proofs.—Diseases chronic and acute.—Differences
 of diseases in each simple system.—Two classes of symptoms in the
 local affections.—Their difference.—Varieties of the pain, heat,
 &c. according to the systems.—What should be understood by acute
 and chronic affections in the simple systems.—Influence of these
 considerations upon morbid anatomy.—Defects of the old divisions.—New
 manner of considering morbid anatomy.                                49


 VIII. _Remarks upon the Classification of the Functions._

 Table of this classification.                                        60


 SYSTEMS COMMON TO ALL THE APPARATUS.


 _General Observations._

 Division of the systems.—Systems common to all the apparatus.—Their
 characters.—They form the nutritive parenchyma of the organs.—Remarks
 upon nutrition.—Diversity of the nutritive substances.               77




 CELLULAR SYSTEM.


 General Remarks.—Division.                                           87


 ARTICLE FIRST.

 OF THE CELLULAR SYSTEM CONSIDERED IN RELATION TO THE ORGANS.


 I. _Of the Cellular System exterior to each Organ._

 Division of the organs in relation to the neighbouring texture.      88

 _Of the Cellular System which adheres only to one side of the organs._

 _Sub-cutaneous cellular texture._—Arrangement of this texture,
 1st, upon the median line; 2d, in the different regions of the
 body.—Varieties of density and laxity. Uses of the sub-cutaneous
 texture.—Its fluids.                                                 88

 _Sub-mucous cellular texture._—Difference of this texture from the
 preceding.—The density of that.—Consequences.

 _Sub-serous cellular texture._—It is in general loose and
 abundant.—Why.—Place where it is dense.                              92

 _Cellular texture exterior to the arteries._—Its peculiar nature is
 analogous to that of the sub-mucous texture.—Its relations with the
 arterial fibres.

 _Cellular texture exterior to the veins._—It is analogous to the
 preceding, only less thick.—Remarks.

 _Cellular texture exterior to the excretory ducts._—The same structure
 and arrangement as in the preceding.                                 96

 _Of the cellular system considered in relation to the organs that
 it surrounds on all sides._—Cellular atmosphere.—Fluids of this
 atmosphere.—Insulation of the vitality of the organs.—Of this
 atmosphere considered as a means for the propagation of diseases.—It
 favours the motion of the parts.                                     96


 II. _Of the Internal Cellular System of each Organ._

 Arrangement of this texture.—Its uses.—Its different proportions.   102




 ARTICLE SECOND.

 OF THE CELLULAR SYSTEM CONSIDERED INDEPENDENTLY OF THE ORGANS.


 I. _Of the Cellular System of the Head._

 _Cellular texture of the cranium._—It is almost nothing within.—Its
 communications.—Consequences of these communications.—It is more
 abundant without.

 _Cellular texture of the face._—It is very abundant.—Its uses.—Its
 communications, &c.                                                 104


 II. _Of the Cellular System of the Trunk._

 _Vertebral cellular texture._—It is not abundant in the cavity of
 the canal.—On the exterior, there is but little behind, and more in
 front.—Consequences.

 _Cervical cellular texture._—It is abundant.—Its
 communications.—Consequences.

 _Pectoral cellular texture._—It is found especially upon the median
 line.—Its communications.—External texture.

 _Abdominal cellular texture._—Of the parts in which it is most
 abundant.—Its communications.

 _Cellular texture of the pelvis._—It is very
 abundant.—Why.—Consequences.—Its communications.                    108


 III. _Of the Cellular System of the Extremities._

 Its different proportions in the superior and the inferior.         112


 ARTICLE THIRD.

 OF THE FORMS OF THE CELLULAR SYSTEM, AND THE FLUIDS IT CONTAINS.


 I. _Of the Cells._

 Their form.—Their capacity.—Their communication.—-Experiments.—Of the
 cellular permeability.—In what sense it should be understood.       114


 II. _Of the Serum of the Cellular Membrane._

 Proof of its existence.—Its evaporation.—It varies in the
 different regions.—Method of ascertaining the proportions of
 it.—Experiments.—Nature of this fluid.—Experiments.                 117


 III. _Of the Cellular Fat._

 _Natural proportions of the fat._—Varieties of its proportions
 according to the regions, organs, systems, &c—Its peculiar arrangement
 in childhood.—Varieties according to the other ages.                119

 _Unnatural proportions of fat._—Its preternatural abundance indicates
 weakness.—Different proofs.—Of the causes of the diminution of
 fat.—Remark upon this diminution.                                   121

 _Different states of the fat._—Its degree of fluidity is not
 during life in proportion to temperature.—Its consistence in young
 animals.—Consequences.—Its alterations by age, diseases, &c.        125

 _Exhalation of fat._—Different opinions.—The fat is
 exhaled.—Proofs.—Nature of this fluid.—Relation of its uses with the
 places where it exists and with those in which it is wanting.       127


 ARTICLE FOURTH.

 ORGANIZATION OF THE CELLULAR SYSTEM.


 I. _Texture peculiar to the organization of the Cellular System._

 Filaments and layers from which it results.—Method of seeing them
 to advantage.—Their nature.—Essential difference in the cellular
 organization.—There are two species of cellular texture.            129

 _Composition of the cellular texture._—Experiments upon this
 texture.—Action of the air, water, caloric and the gastric
 juices.—Experiments.—Of the gases sometimes extricated in the cellular
 texture.                                                            132


 II. _Parts common to the Organization of the Cellular Texture._

 _Blood vessels._—The inaccuracy of injections in demonstrating them.

 _Exhalants._—Of the cellular exhalations.—Proofs and phenomena of
 these exhalations.

 _Absorbents._—Cellular absorptions.—Proofs.—The cellular texture is
 not wholly formed of absorbents.

 _Nerves._                                                           136




 ARTICLE FIFTH.

 PROPERTIES OF THE CELLULAR SYSTEM.


 I. _Properties of Texture._

 _Extensibility._—Examples of the different distensions.—Distinctive
 character of the cellular extensibility.—Its phenomena.—It becomes
 nothing in inflammation, chronic engorgements, &c.

 _Contractility._—Different examples of this property brought into
 action.—Its varieties according to the ages.—General remarks.       140


 II. _Vital Properties._

 The animal ones are inconsiderable.—The organic are greater, except
 sensible contractility, which however exists to a certain extent.

 _Sympathies._—It is necessary to distinguish them from the phenomena
 of juxta-position.—Various examples.—General observations.—Vital
 properties put in action by the sympathies.

 _Character of the vital properties._—The vital activity is very
 considerable in the cellular texture.—Various proofs.—Remarks upon
 the species.—Difference of vitality in the two species of cellular
 texture.                                                            143


 III. _Properties of Reproduction._

 _Influence of the cellular texture upon the formation of
 cicatrices._—Division of the periods of the cicatrices.

 _First period._—Inflammation.—How it takes place.—Its advantages.

 _Second period._—Fleshy granulations.—Experiments.—Provisional
 membrane of the cicatrices.—Its uses.—General phenomena of the
 internal cicatrices.—Cellular nature of this membrane and of the
 granulations.—Different opinions.

 _Third period._—Suppuration.—What corresponds to it in the internal
 cicatrices.—Analogy of these cicatrices with the external.

 _Fourth period._—Contraction of the fleshy
 granulations.—Adhesions.—Consequences of the preceding principles.—Of
 union by the first intention.                                       148


 _Influence of the cellular texture in the formation of
 tumours._—Cellular nature of all tumours which grow and
 increase.—Proofs.—Mode of development of these tumours.—How they
 differ from various engorgements, acute and chronic.                157

 _Influence of the cellular texture in the formation of cysts._—What
 is a cyst.—Its analogy with the serous surfaces.—Its cellular
 structure.—Mode of its development.                                 160


 ARTICLE SIXTH.

 DEVELOPMENT OF THE CELLULAR TEXTURE.


 I. _State of the Cellular System in the First Age._

 Mucous mass represented by the cellular texture of the
 fœtus.—Superabundance of fluid.—This is then the cellular
 fluid.—Difficulty of emphysema in the fœtus.—State of the cellular
 texture in infancy and youth.—Its vital energy.—Consequences.       164

 II. _State of the Cellular System in the After Ages._

 Arrangement of the cellular texture in the adult.—Differences arising
 from sex.—Degeneracy of this texture in old age.—Withering that it
 experiences.—Consequences.                                          167


 NERVOUS SYSTEM OF ANIMAL LIFE.

 Division of the nerves into two systems.—Differences of these
 two systems.—General arrangement of that of animal life.—Its
 symmetry.—Relation of size between the nerves and the brain.        169


 ARTICLE FIRST.

 EXTERNAL FORMS OF THE NERVOUS SYSTEM OF ANIMAL LIFE.


 I. _Origin of the Cerebral Nerves._

 In what sense this origin must be understood.—It takes place, 1st, in
 the brain; 2d, in the tuber annulare and its dependancies; 3d, in the
 spinal marrow.—Manner of this triple origin.—Of the crossing of the
 nerves.—Phenomena of paralysis in regard to this.—Peculiar arrangement
 of the cerebral membranes at the origin of the nerves.—Extent,
 direction and form of the nerves at this origin.                    171


 II. _Course of the Cerebral Nerves._

 _Communications of the cerebral nerves at their exit from
 their osseous cavity._—There are none between the nerves of
 the brain properly called.—The communications begin in those
 of the tuber annulare.—They are very numerous in those of the
 spinal marrow.—Arrangement of the plexuses which result from
 them.—Consequences as it regards descriptive neurology.

 _Internal communications of the nervous cords._—Manner
 of these communications.—Internal plexus to each
 nerve.—Consequences.—Difference from anastomoses.

 _Nervous Trunks._—Their course.—Their form.—Their length, &c.

 _Nervous branches, smaller branches, ramifications, &c._—Mode of
 origin.—Length.—Course, &c.                                         176


 III. _Termination of the Nerves._

 What is to be understood by it.—Triple mode of termination.

 _Anastomoses with the same system._—What is to be understood by
 anastomoses.—They are rare in this system.—They can be referred to
 three classes.

 _Anastomoses with the system of organic life.—Termination in the
 organs._—Manner of this termination.—Division of the organs in this
 respect.                                                            182


 ARTICLE SECOND.

 ORGANIZATION OF THE NERVOUS SYSTEM OF ANIMAL LIFE.


 I. _Texture peculiar to this Organization._

 Arrangement of the nervous cords.—Their varieties.—Each nerve has its
 peculiar organization.—Of the structure of the nervous filaments.


 _Of the nervous coat and its origin._—How this origin may be seen.—Its
 triple arrangement at the brain, the tuber annulare and the spinal
 marrow.—Particular arrangement of the optic nerve.—Remarks upon the
 pia mater.—Course of the nervous coat.                              185

 _Action of certain substances upon the nervous coat; its resistance,
 &c._—Action of the acids, water, caloric, and the alkalies.—Resistance
 of the nervous coat.

 _Medullary substance_; its origin, arrangement and proportions.

 _Comparison between the medullary substance of the brain and the
 nerves._—Effect of desiccation upon each.—Putrefaction and its
 phenomena.—Absence of the horny hardening in both.—Action of water
 upon both.—Action of the acids, the alkalies, neutral salts and the
 digestive juices.—Difference of the nervous pulp in each part.      190


 II. _Parts common to the Organization of the Nervous System of Animal
 Life._

 _Cellular texture._—It is wanting in the nerves, in the cranium
 and the spine. Elsewhere it is found between their filaments and
 cords.—Cellular fat.

 _Blood vessels._—Their arrangement.—Remarks upon the veins.—Of the
 blood.—Of the nerves.—Action of this fluid upon them.

 _Exhalants and Absorbents._—Examination of the opinion upon the
 exhalation of the nervous coat.—Different observations.

 _Nerves._                                                           199


 ARTICLE THIRD.

 PROPERTIES OF THE NERVOUS SYSTEM OF ANIMAL LIFE.


 I. _Properties of Texture._

 They are but very slightly marked.—Remarks upon the nervous
 distensions.                                                        204


 II. _Vital Properties.—Properties of Animal Life._

 _Animal sensibility inherent in the nerves._—Various experiments
 upon this sensibility.—Remarks upon that of the brain.—Phenomena
 of the experiments upon the nerves.—Character of the animal
 nervous sensibility. —Of neuralgias.—Another character of this
 sensibility.—Experiments.—Consequences.                             206

 _Influence of the nerves upon the animal sensibility of all the
 organs._—Distinction of the sensations, in this respect, into
 external and internal.—Subdivision of the external into general
 and particular.—Part which the nerves perform in each.—Internal
 sensations.—Uncertainty respecting the nervous influence
 in sensations.—Differences between animal sensibility and
 contractility.—Of the nervous atmosphere.—Uncertainty of this
 opinion.                                                           211

 _Animal contractility.—Influence of the nerves upon that of the other
 parts._—How the nerves are the agents of this property.—Different
 opinions upon the action of the nerves.—Uncertainty of these
 opinions.—General observations.

 _Properties of organic life, considered in the nerves._—They are
 slightly marked.—Increase of the size of the nerves in the affections
 of some parts.—Various experiments and observations.

 _Influence of the cerebral nerves upon the organic properties of
 the other parts._—They are foreign to these properties.—They have
 not there any known influence, 1st, upon the capillary circulation;
 2d, upon exhalation; 3d, upon secretion; 4th, upon absorption;
 5th, upon nutrition.—Different proofs of these assertions.—Remarks
 on the diseases which affect animal life and those which affect
 organic.—Uncertainty of the term _nervous influence_.               216

 _Sympathies.—Sympathies peculiar to the nerves._—Different phenomena
 of these sympathies.—Sympathies, 1st, between two nerves of the
 same pair; 2d, between two nerves of the same side; 3d, between the
 branches of the same pair; 4th, between the nerves and different
 organs.—Different examples of these sympathies.                     224

 _Influence of the nerves upon the sympathies of the other
 organs._—Different opinions upon sympathies.—Uncertainty of these
 opinions.—Division of sympathies founded upon that of the vital
 properties.—Different influence of the nerves upon each species of
 sympathy.—Cases in which it is real and those in which it is
 nothing.                                                           226


 III. _Properties of Reproduction._

 Phenomena of nervous cicatrizations.—Their analogy with other
 cicatrizations.                                                     233




 ARTICLE FOURTH.

 DEVELOPMENT OF THE NERVOUS SYSTEM OF ANIMAL LIFE.


 I. _State of this System in the Fœtus._

 It is much developed.—General remarks.—Inactivity of the brain,
 notwithstanding its development.—Its softness.—Action of the
 alkalies upon this organ.—The cerebral nerves are developed in
 proportion.—Peculiar phenomenon of their development.—This phenomenon
 is opposite to that of the arteries.—Consequence which results from
 it.                                                                 235


 II. _State of the Nervous System during Growth._

 Phenomena at birth.—Influence of the red blood.—Predominance of
 the nervous system during childhood.—Consequences relative to the
 sensations, motions and various affections.                         240


 III. _State of the Nervous System after Growth._

 Phenomenon of puberty.—Phenomena of the following ages.             244


 IV. _State of the Nervous System in Old Age._

 Its action is slight.—State of the brain at this period.—Influence of
 this state upon sensibility.—Phenomena of sensation and motion in old
 age.                                                                244


 NERVOUS SYSTEM OF ORGANIC LIFE.

 GENERAL REMARKS.

 How this system should be understood.—The great sympathetic does not
 exist.—Each ganglion forms an insulated system.—This system belongs to
 organic life.—It exhibits many irregularities.—The mode of describing
 it.                                                                 249




 ARTICLE FIRST.

 OF THE GANGLIONS.

 I. _Situation, Forms, Relations, &c._

 Ganglions that are constant.—Those that are accidental.             253


 II. _Organization._

 Colour.—Difference of the texture of the ganglions from that of the
 brain.—Comparative experiments.—This texture is not fibrous.—It
 differs essentially from that of the nerves.—Its organic lesions are
 rare.—Common parts of this texture.                                 255


 III. _Properties._

 The ganglions have the organic ones.—The animal appear to be slightly
 marked in them.—Experiments.—Sympathies.—Nervous affections of the
 ganglions.—The kind of pain of this system.—General remarks.        260


 IV. _Development._

 It does not follow that of the brain.—Influence of this fact upon the
 diseases of childhood.—Another difference between the ganglions and
 the brain.                                                          263


 V. _Remarks upon the Vertebral Ganglions._

 Their arrangement.—Obscurity which they throw upon the functions of
 this system.                                                        264


 ARTICLE SECOND.

 OF THE NERVES OF ORGANIC LIFE.


 I. _Origin._

 Manner of this origin.—Method of seeing it.                         265


 II. _Course, Termination, Plexuses._

 Of the branches which go to the cerebral nerves.—Of those which go to
 the neighbouring ganglions.—Of those which go the muscles.—Of those
 which form the plexuses.—Arrangement of these last.—Of the filaments
 which go from them.—Their double arrangement upon the arteries.     267


 III. _Structure, Properties, &c._

 Analogy with the preceding nerves as to texture.—Animal sensibility
 appears to be less in them.—Experiments.—Sympathies of these
 nerves.—General remarks.                                            271


 VASCULAR SYSTEM WITH RED BLOOD.


 ARTICLE FIRST.

 GENERAL REMARKS UPON THE CIRCULATION.


 I. _Division of the Circulation._

 _Circulation of red blood._—General organs.—Direction.

 _Circulation of black blood._—General organs.—Direction.

 _Difference of the two circulations._—Their separation is
 complete.—Opposition of the lungs to all the parts.

 _General mechanical phenomena of the two circulations._—Conical
 form of the circulatory apparatus.—There are two cones for each
 circulation.—The heart is placed at their union as a double agent of
 impulse.—Its inequality in this respect.                            275


 II. _Reflections upon the General Uses of the Circulation._

 _General uses of the circulation of the red blood._—It furnishes the
 materials of secretion, exhalation, absorption, &c.—All the great
 phenomena of the economy are derived from it.

 _General uses of the circulation of black blood._—It repairs
 the losses made by the preceding, by the substances which it
 receives.—General and opposite attributes of the two—sanguineous
 systems.                                                            282




 ARTICLE SECOND.

 SITUATION, FORMS, AND GENERAL ARRANGEMENT OF THE VASCULAR SYSTEM WITH
 RED BLOOD.

 Of the two portions of this system.—Of their union.—Position of the
 agent of impulse compared to the whole body.                        285


 I. _Origin of the Arteries._

 _Origin of the aorta._—Peculiar anatomical arrangement of this
 origin.                                                             287

 _Origin of the trunks, branches, smaller branches, &c._—Number of the
 arterial divisions.—Angles of origin.—Proportion of the divisions.  288


 II. _Course of the Arteries._

 _Course of the trunks and branches._—Their position, relation and
 direction.—Motions which they communicate.                          291

 _Course of the smaller branches, ramifications,
 &c._—Position.—Relations.—Curvatures.—These curvatures have no
 influence upon the motion of the blood.—Proofs.—Uses of these
 curvatures.                                                         293

 _Anastomoses of the arteries in their course._—Of the two modes
 of anastomoses.—Triple mode of those in which two equal trunks
 terminate.—Anastomoses with unequal trunks.—General remarks upon
 anastomoses.                                                        296

 _Forms of the arteries in their course._—In what direction they are
 conical.—Relation of capacities.                                    299


 III. _Termination of the Arteries._

 It takes place in the capillary system.—Its varieties according to the
 organs.                                                             300


 ARTICLE THIRD.

 ORGANIZATION OF THE VASCULAR SYSTEM WITH RED BLOOD.


 I. _Texture peculiar to this Organization._

 Two principal membranes form it.                                    301

 _Peculiar membrane of the
 arteries._—Thickness.—Colour.—Experiments.—Varieties in the
 cerebral arteries.—Arterial fibres.—Arrangement of these fibres at
 the origin of the branches.—Their nature is not muscular.— Their
 brittleness.—Their resistance.—General consequences.                302

 _Action of different agents upon the arterial
 texture._—Desiccation.—Putrefaction.—Maceration.—Stewing.—Action of
 the acids, the alkalies, &c.                                        308

 _Membrane common to the system with red blood._—Its differences in the
 different regions.—Of the fluid which moistens it.—Its relations.—Its
 nature.—Its singular disposition to ossification.—Peculiar phenomena
 and laws of this ossification.—Pathological consequences.           311


 II. _Parts common to the Organization of the Vascular System with Red
 Blood._

 _Blood vessels._—Their arrangement.—They do not appear to go to the
 internal membrane.                                                  317

 _Cellular texture._—There are two species of it.—Of that which unites
 the artery to the neighbouring organs.—Of that which is peculiar
 to it, and which has a peculiar nature.—The arterial fibres are
 remarkable for having none of this texture between
 them.—Consequences.                                                 318

 _Exhalants and absorbents._—There does not appear to be absorption in
 the arteries.—Experiments.                                          321

 _Nerves._—Of the cerebral ones.—Of the organic ones.—Their
 proportion.—Their course, &c.                                       324


 ARTICLE FOURTH.

 PROPERTIES OF THE VASCULAR SYSTEM WITH RED BLOOD.


 I. _Physical Properties._

 Remarkable elasticity.—Its use.—Its differences from contractility of
 texture.                                                            322


 II. _Properties of Texture._

 _Extensibility._—1st, of that in the axis; 2d, of that in the
 diameter.                                                           324

 _Contractility._—Of that in the axis.—Of that in the
 diameter.—Its differences from irritability.—Remarks upon this
 contractility.—Practical consequences.                              326




 III. _Vital Properties. Properties of Animal Life._

 _Sensibility._—Experiments upon this property.                      329

 _Contractility._—It is nothing. _ib._

 _Properties of organic life.—Sensible organic Contractility._—It is
 nothing.—Different experiments to prove it.—Mistakes concerning this
 property.                                                           330

 _Insensible organic contractility._—How its influence must
 be understood.—Vital activity is but slightly marked in the
 arteries.—General consequences.                                     332

 _Remarks upon the causes of the motion of the red blood._—These causes
 appear to be foreign to the arteries.                               335

 _Influence of the heart in the motion of red blood._—Different
 proofs of this influence.—Morbid phenomena.—Different
 experiments.—Observations.—General Consequences.                    336

 _Of the limits of the action of the heart._—They appear to be at the
 place of the change of the red blood into black.—Increasing influence
 of the arteries upon the red blood in the neighbourhood of the
 capillaries.                                                        342

 _Phenomena of the impulse of the heart._—The motion of the red blood
 is sudden and instantaneous.—Proofs.—The contraction of the arteries
 does not push the blood.—From what it arises.—The causes of delay are
 nothing.—General remarks.                                           334

 _Remarks upon the pulse._—The arterial locomotion has a great part in
 it.—Of the accessory causes.—Of the varieties of the pulse.—General
 reflections.                                                        348

 _Sympathies._—They are in general rare in the arteries.—Why.        352


 ARTICLE FIFTH.

 DEVELOPMENT OF THE VASCULAR SYSTEM WITH RED BLOOD.


 I. _State of this System in the Fœtus._

 The two systems are then confounded.—There is but one species of
 blood.—How the fœtus can live with black blood alone.—Peculiar
 mode of circulation in the fœtus.—Consequences which result from
 it.—Insensible change of this mode of circulation.—How it takes
 place.—Great development of the arteries in the fœtus.              354




 II. _State of the Vascular System with Red Blood during Growth._

 Sudden formation of the red blood at birth.—Changes in the course of
 this fluid.—Phenomena and causes of these changes.—Predominance of the
 arteries during youth.                                              364


 III. _State of the Vascular System with Red Blood after Growth._

 Influence of the genital organs.—Varieties of the influence of the red
 blood according to the ages.                                        371


 IV. _State of the Vascular System with Red Blood during old Age._

 Diminution of the arterial ramifications.—The red blood is less
 abundant.—The arteries are condensed.—Phenomena of the pulse.—Of the
 pulse in the last moments of life.—Experiments upon this subject.   373


 V. _Accidental Development of the System with Red Blood._

 There are two kinds of it; 1st, Dilatation from an obstacle. 2d,
 Dilatation from any tumour.                                         377


 VASCULAR SYSTEM WITH BLACK BLOOD.


 GENERAL OBSERVATIONS.


 ARTICLE FIRST.

 SITUATION, FORMS, DIVISION AND GENERAL ARRANGEMENT OF THE VASCULAR
 SYSTEM WITH BLACK BLOOD.


 I. _Origin of the Veins._

 Manner of this origin.—Two orders of veins.                         380


 II. _Course of the Veins._

 Examination of this course on the exterior and the interior.        381

 III. _Proportion of the capacity of the two systems with Black and Red
 Blood._

 Remarks upon the varieties of venous capacity.—Parallel between
 the two vascular apparatus with red and black blood in this
 respect.—General consequences.—The velocity is in an inverse ratio of
 the capacity, &c.                                                   382

 _Ramifications, small branches, branches, angles of union, &c.—Forms
 of the Veins._—In what direction these vessels are conical.—Relations
 between the branches and their divisions.                           388

 _Anastomoses._—They are very frequent.—Why.—Communication between the
 external and the internal order.—Consequences.—Different modes of
 anastomoses.—Their necessity from the numerous obstacles to the course
 of the blood.—Of these obstacles.                                   392


 IV. _Termination of the Veins._

 Mode of termination in the heart.—Of the two venous cones, the
 superior and the inferior.—Of their communication by the azygos.    396


 ARTICLE SECOND.

 ORGANIZATION OF THE VASCULAR SYSTEM WITH BLACK BLOOD.


 I. _Texture peculiar to this Organization._

 _Membrane peculiar to the veins._—Manner of seeing it.—Its
 longitudinal fibres.—Varieties of these fibres.—Their nature.—Peculiar
 arrangement of the cerebral sinuses.                                399

 _Common membrane of the black blood._—Its differences from that of
 the red blood.—More extensibility.—Less thickness.—No disposition to
 ossify.—Consequences.                                               403

 _Of the valves of the veins._—Their form.—Their situation.—Veins which
 they occupy.—Their size.—Remarks upon their relations with the caliber
 of the veins.—Their variety.—Their number.                          404

 _Action of reagents upon the venous texture._—Action of the air,
 water, caloric, the acids, &c.                                      407


 II. _Parts common to the Organization of the Vascular System with
 Black Blood._

 _Blood vessels. Cellular texture._—Of that which unites the veins to
 the neighbouring parts.—Of that which is peculiar to them.          408


 _Exhalants and Absorbents._—Experiments upon venous absorption.

 _Nerves._—There are but very few of them.                           409


 ARTICLE THIRD.

 PROPERTIES OF THE VASCULAR SYSTEM WITH BLACK BLOOD.


 I. _Properties of Texture._

 _Extensibility._—It is very evident.—Venous ruptures however take
 place.—Various examples.—Their causes are but obscurely known.      411

 _Contractility_—Of this property in the longitudinal and the
 transverse direction.                                               413


 II. _Vital Properties._

 _Properties of Animal Life._—Result of the experiments upon
 sensibility.—There is no contractility.                             414

 _Properties of organic life. Sensible Contractility._—It appears to be
 but slight.—General remarks.                                        415

 _Of the venous pulse._—Of its cause.—It is a reflux.—Double cause
 which produces it.                                                  416

 _Insensible Contractility._—It appears to exist.—The vital activity is
 greater in the veins than in the arteries.—Consequences.            419

 _Observations on the motion of the black blood in the veins._—There is
 no pulse analogous to that of the arteries.—Agent of impulse of the
 venous blood.—Causes of delay—Accessory causes of motion.—Resemblance
 between the motion of the veins and that of the arteries.           420

 _Sympathies_ of the veins.—They are very obscure.                   424


 ARTICLE FOURTH.

 DEVELOPMENT OF THE VASCULAR SYSTEM WITH BLACK BLOOD.


 I. _State of this System in the Fœtus._

 The veins are less developed in proportion than the
 arteries.—Why.—Remarks.                                             425




 II. _State of this System during Growth and afterwards._

 Various phenomena of childhood, adult age, &c.                      427


 III. _State of this System in Old Age._

 The veins are much developed in old age.—This development is only a
 dilatation.—Its varieties according to different circumstances.     428


 IV. _Accidental Development of the Veins._

 It must be considered, 1st, in tumours; 2d, in the distensions of the
 different parts.                                                    430


 ARTICLE FIFTH.

 REMARKS UPON THE PULMONARY ARTERY AND VEINS.

 Though the two kinds of blood are separate, yet the mechanical
 phenomena of their courses are analogous in the aorta and the
 pulmonary artery, and in the general and the pulmonary veins.      _ib._


 ARTICLE SIXTH.

 ABDOMINAL VASCULAR SYSTEM WITH BLACK BLOOD.

 _Situation, forms, general arrangement, anastomoses, &c._—Origin
 and termination in the capillaries.—Abdominal portion.—Hepatic
 portion.—Differences between them.                                  433

 _Organization, properties, &c._—Analogy with the veins in this
 respect.—Peculiar arrangement in the hepatic portion.—Absence of
 valves.—Why.                                                        436

 _Remarks upon the motion of the black abdominal blood._—Comparison
 between the liver and the lungs.—Their difference as it regards
 the blood that goes to them.—Mechanism of the circulation of this
 system.—Influence of the accessory causes.                          438

 _Remarks upon the liver._—It performs another function besides the
 secretion of bile.—Proofs.—We are ignorant of this function.—It
 must be extremely important.—Various proofs.—The liver exhibits
 phenomena that no other gland does.—It is not certain that the black
 abdominal blood serves for the secretion of bile.—Proofs.—General
 observations.—Experiments.                                          440

 _Remarks upon the course of the bile._—Course of this fluid during
 abstinence and during digestion.—Cystic bile.—Hepatic bile.—Reflux
 towards the stomach during vacuity and fulness.—Experiments.        446

 _Development._—There is only one vascular system in the fœtus.—It
 is divided into three at birth.—State of the umbilical vein and
 the vena porta in the fœtus.—Relative size of the liver at this
 period.—Phenomena at birth.—Different influences of this system in the
 following ages.                                                     450


 END OF CONTENTS TO VOL. I.




 VOLUME SECOND.


 CAPILLARY SYSTEMS.

 PAGE.

 There are two of them.—Their general arrangement.—Their opposition.   3


 ARTICLE FIRST.

 OF THE GENERAL CAPILLARY SYSTEM.

 General arrangement of this system.                                   4


 I. _General division of the Capillaries._

 _Of the organs in which the capillaries contain only blood._          6

 _Of the organs in which the capillaries contain blood and fluids
 differing from it._—Serous system taken for an example.—Experiments by
 injections.—Various other systems present analogous facts.—Proportion
 of the blood and the fluids differing from it. _ib._

 _Of the organs in which the capillaries do not contain blood._        8


 II. _Difference of Organs in respect to the number of their
 Capillaries._

 There are many classes of organs in this respect.—Why the capillaries
 are very much developed in some.—Consequences as it regards diseases. 9

 _Remarks upon injections._—Their insufficiency in making us acquainted
 with the small vessels.                                              10


 III. _Of the proportions which exist in the Capillaries between the
 Blood and the Fluids that differ from it._

 Continual varieties in the proportion.—Cause of these varieties.—They
 are very numerous.                                                   12


 _Different proportions of blood in the capillaries, according as the
 secretions and exhalations are active or passive._—Of active and
 passive exhalations.—Of secretions of the same nature.—Examination
 of each.—Proofs that wherever there is activity, blood enters the
 capillaries.—Opposite arrangement in the passive phenomena.          13

 _Consequences of the preceding Remarks._                             17


 IV. _Of the Anastomoses of the General Capillary System._

 Mode of these anastomoses.—The capillaries considered in relation
 to the vessels with which they communicate.—Influence of these
 communications.—Important observation in regard to the examination of
 dead bodies.—How acute inflammations disappear at death.             17


 V. _How, notwithstanding the general communication of the Capillary
 System, the Blood and the Fluids differing from it, remain separate._

 This depends on the different modifications of the organic
 sensibility.—Proofs.—General remarks.                                21


 VI. _Consequences of the preceding principles, in relation to
 Inflammation._

 Every thing arises, in this affection, from the alteration of the
 organic sensibility.—Proofs.—Varieties of intensity and nature in
 inflammations.—Terminations of inflammations.—Of putrefaction.—Of
 death.—Of induration.—Of the blood which stops in inflamed parts.    24

 _Differences of inflammation according to the different systems._—Each
 has a peculiar one.—Of those which are the most disposed to it.—It
 has peculiar modifications in each.—Same observation in regard to its
 terminations.                                                        30


 VII. _Structure and Properties of the Capillaries._

 We cannot ascertain completely the structure.—It has however
 varieties.                                                           33


 VIII. _Of the Circulation of the Capillaries._

 _Motions of the fluids in the Capillary System._—The blood is
 independent of the action of the heart in the capillaries.—Various
 proofs of this assertion.—The blood circulates by the influence
 of the forces of the part.—Varieties of the motions.—Causes of
 these varieties.—Influence of the atmosphere upon the capillary
 circulation.—Of the two kinds of bleeding in relation to the
 capillaries and to the trunks.—Circulation of other fluids than the
 blood in the capillaries.                                            34

 _Phenomena of the alteration of the fluids in the Capillary
 System._—Change of the red blood to black.—Phenomena of this change. 41


 IX. _Of the Capillaries considered as the seat of the production of
 Heat._

 Different hypotheses.—Phenomena of animal heat.—How it is
 produced.—Analogy of the production of heat with exhalation,
 secretion, &c.—Influence of the different vital forces.—Explanation
 of the phenomena of animal heat in the state of health and
 disease.—Sympathetic heat.—Sympathies of heat.—Difference between the
 two.                                                                 43


 ARTICLE SECOND.

 PULMONARY CAPILLARY SYSTEM.


 I. _Relation of the two Capillary Systems, Pulmonary and General._

 How all the blood of the general system can go through the
 pulmonary.—Difference of one from the other as it respects the course
 of this fluid.                                                       55


 II. _Remarks upon the Circulation of the Pulmonary Capillaries._

 Peculiar character of pulmonary inflammations.—Phenomena to which they
 give rise.—Of the pulmonary circulation in various other diseases.   58


 III. _Alteration of the Blood in the Pulmonary Capillaries._         63


 IV. _Remarks upon the state of the Lungs in Dead Bodies._

 Their proportions very various from engorgement.—They are hardly ever
 in the natural state.—Why.—Consequences.                             64




 EXHALANT SYSTEM.

 General Remarks upon the differences of exhalations and absorptions. 67


 ARTICLE FIRST.

 GENERAL ARRANGEMENT OF THE EXHALANTS.


 I. _Origin, Course and Termination._

 Different hypotheses respecting these vessels.—What observation shows
 us concerning them.                                                  69


 II. _Division of the Exhalants._

 They can be referred to three classes.—Table of these classes and
 their division.                                                      71

 III. _Difference of the Exhalations._                                73


 ARTICLE SECOND.

 PROPERTIES, FUNCTIONS AND DEVELOPMENT OF THE EXHALANT SYSTEM.


 I. _Properties._

 We are ignorant of those of texture.—The organic are very evident in
 it.                                                                  74

 _Characters of the Vital Properties._—They vary in each
 system.—Consequences as it regards functions. _ib._


 II. _Of Natural Exhalations._

 They are all derived from the vital properties.—They vary consequently
 like these properties.—Proofs.—Of sympathetic exhalations.           75




 III. _Of Preternatural Exhalations._

 _Sanguineous exhalation.—Hemorrhage of the excrementitious
 exhalants._—Hemorrhage from the skin.—Hemorrhages from the mucous
 surfaces.—They take place by exhalation.—Proofs.—Experiments.—Of
 active and passive hemorrhages.—Differences between hemorrhages by
 rupture and by exhalation, between those of the capillaries and those
 of the great vessels.                                                78

 _Hemorrhages of the recrementitious exhalants._—Hemorrhages of the
 serous surfaces.—Observations concerning dead bodies.—Cellular
 hemorrhages.—Other hemorrhages of the exhalants.                     85

 _Preternatural exhalations, not sanguineous._—Varieties of the
 exhaled fluids, according to the state of the vital forces of the
 exhalants.—Different examples of these varieties.                    87


 IV. _Of the preternatural development of the exhalants._

 It is especially in cysts that it takes place.—The secreted fluids are
 never preternaturally poured out like the exhaled.—Why.—Of the natural
 emunctories.                                                         88


 ABSORBENT SYSTEM.


 GENERAL OBSERVATIONS.


 ARTICLE FIRST.

 OF THE ABSORBENT VESSELS.


 I. _Origin of the Absorbents._

 Table of absorptions.—Of external absorptions.—Of internal
 absorptions.—Of the nutritive absorptions.—It is impossible to know
 the mode of origin of the absorbents.—Interlacing of the branches.  91


 II. _Course of the Absorbents._

 Their division into two layers, superficial and deep-seated.—Their
 arrangement in the extremities and the trunk.                        95


 _Forms of the absorbents in their course._—They are cylindrical, full
 of knots, &c.—Consequences of these forms.—The absorbents have not as
 great capacity during life as in the dead body.                      97

 _Of the capacity of the absorbents in their course._—Manner of
 ascertaining it.—Extreme varieties which it exhibits.—Capacity of the
 absorbents compared with that of the veins.                          99

 _Anastomoses of the absorbents in their course._—Different modes of
 these anastomoses.—Remarks upon the lymphatic circulation.          102

 _Remarks upon the difference of dropsies that are produced by the
 increase of exhalation, and those that are the effect of a diminution
 of absorption._—Cases that may be referred to one or the other
 cause.                                                              104


 III. _Termination of the Absorbents._

 Trunks of termination.—Their disproportion with the
 branches.—Consequences.—Difficulties in regard to the motion of the
 lymph.—Remarks upon venous absorption.                              105


 IV. _Structure of the Absorbents._

 Exterior texture.—Vessels.—Peculiar membrane.—Valves.—Uses of these
 last.                                                               109


 ARTICLE SECOND.

 LYMPHATIC GLANDS.


 I. _Situation, Size, Forms, &c._

 Varieties of their number and situation in the different
 regions.—Relation with the cellular texture.—Varieties from age, sex,
 &c.                                                                 111


 II. _Organization._

 _Colour._—Its varieties.—Particular arrangement about the bronchia. 114

 _Common parts._—External cellular texture.—Cellular
 membrane.—Vessels.                                                  115

 _Peculiar texture._—Density.—Cells.—Contained fluid.—Properties and
 phenomena of this texture.—Interlacing of the absorbents.           116




 ARTICLE THIRD.

 PROPERTIES OF THE ABSORBENT SYSTEM.


 I. _Properties of Texture._                                         118


 II. _Vital Properties._

 Animal sensibility.—Its phenomena in the vessels and the
 glands.—Organic properties.—Their duration after death.—Remarks upon
 the absorbent faculty of dead bodies.                               119

 _Characters of the vital properties._—Life is very evident in this
 system.—Its disposition to inflammation.—Character which this
 affection has in it.                                                122

 _Differences of the vital properties in the absorbent vessels and
 their glands._—These differences are remarkable.—Their influence upon
 diseases.                                                           123

 _Sympathies._—Sympathies of the glands.—Sympathies of the
 vessels.—Remarks upon the engorgements of the lymphatic glands.     124


 ARTICLE FOURTH.

 OF ABSORPTION.


 I. _Influence of the Vital Forces upon this Function._

 All depends on the organic properties.                              128


 II. _Varieties of Absorption._

 Different examples.—Of resolution.—Of the absorption of morbific
 principles.                                                         129


 III. _Motion of the Fluids in the Absorbents._

 Laws of this motion.—It is not subject to any reflux.—Why.          132


 IV. _Of Absorption in the different Ages._

 It appears that the internal and external absorptions are opposite at
 the two extreme ages.—Remarks.                                      134




 V. _Preternatural Absorption._

 Absorption of certain fluids different from those naturally
 absorbed.—Absorption in the cysts.                                  138


 SYSTEMS PECULIAR TO CERTAIN APPARATUS.


 GENERAL OBSERVATIONS.

 Differences of the systems peculiar to certain apparatus, from those
 common to all.—Characters of the first.—Their distribution in the
 apparatus.                                                          139


 OSSEOUS SYSTEM.


 GENERAL OBSERVATIONS.


 ARTICLE FIRST.

 OF THE FORMS OF THE OSSEOUS SYSTEM. DIVISION OF THE BONES.


 I. _Of the Long Bones._

 Relation of their position with their general uses.—External forms of
 the body and the extremities.—Internal forms.—Medullary canal.—Its
 situation, extent and form.—Its use.—It disappears in the first
 periods of callus.—It is shorter in proportion in childhood.        144


 II. _Of the Flat Bones._

 Relations of their situation and external forms with the general use
 of forming the cavities.—Internal forms.                            147




 III. _Of the Short Bones._

 Position.—Internal and external forms.—General uses.                149


 IV. _Of the Bony Eminences._

 Their division into those, 1st, of articulation; 2d, of insertion;
 3d, of reflection; 4th, of impression.—Remarks upon each of these
 divisions.—Relations of the second with the muscular force.—How these
 last are formed.                                                    150


 V. _Of the Osseous Cavities._

 Their division into those, 1st, of insertion; 2d, of reception;
 3d, of sliding; 4th, of impression; 5th, of transmission; 6th, of
 nutrition.—Particular remarks upon each division.—Of the three kinds
 of canals of nutrition.                                             153


 ARTICLE SECOND.

 ORGANIZATION OF THE OSSEOUS SYSTEM.


 I. _Texture Peculiar to the Osseous System._

 Common division of this texture.

 _Texture with cells._—How it is formed.—When it is formed.—Of the
 cells and their communications.—Experiments.                        156

 _Compact texture._—Arrangement of its fibres.—Their
 formation.—Experiments to ascertain their direction.—The osseous
 layers do not exist.—Proofs.—Influence of rickets upon the compact
 texture.                                                            158

 _Arrangement of the two osseous textures in the three kinds of
 Bones._—Arrangement of the compact texture.—Two kinds of texture
 with cells in the long bones.—Proportion of the common texture with
 cells and the compact texture in the short and broad bones.—The same
 proportion examined in the cavities and the osseous eminences.      161

 _Of the composition of the osseous texture._—There are two principal
 bases.—Of the saline calcareous substance.—Experiments.—Nature
 of this substance.—Experiments to ascertain the gelatinous
 substance.—Different relations of each of these substances with
 vitality.                                                           164




 II. _Common Parts which enter into the organization of the Osseous
 System._

 Three orders of blood vessels.—Arrangement of
 each.—Experiments.—Proportions according to age.—Communication.—Proofs
 of the existence of the cellular texture.                           167


 ARTICLE THIRD.

 PROPERTIES OF THE OSSEOUS SYSTEM.


 I. _Physical Properties._

 Elasticity.—It is in the inverse ratio of the age.                  171


 II. _Properties of Texture._

 Different examples of contractility and extensibility.—Characters of
 these properties.                                                   171


 III. _Vital Properties._

 They are obscure.                                                   173

 _Characters of these properties._—Slowness of their development.—Their
 influence upon diseases.                                            174

 _Sympathies._—Their character is always chronic.—General remark upon
 sympathies.                                                         175

 _Seat of the vital properties._—They are not seated in the calcareous
 substance.—They exist only in the gelatinous.—Experiment which proves
 it.                                                                 177


 ARTICLE FOURTH.

 OF THE ARTICULATIONS OF THE OSSEOUS SYSTEM.


 I. _Division of the Articulations._

 _Moveable Articulations.—Observations upon their Motions._—1st.
 Opposition; it is extensive or confined.—2d. Circumduction; a motion
 composed of all those of opposition.—3d. Rotation; a motion upon the
 axis.—4th. Sliding.                                                 180


 _Immoveable articulations._—They are on surfaces in juxta-position,
 inserted into each other or implanted.                              182

 _Table of the Articulations._                                       183


 II. _Observations upon the Moveable Articulations._

 _First genus._—Situation.—Form of the surfaces.—Rotation and
 circumduction are inversely in the humerus and the femur.—Why.      184

 _Second genus._—Form of the surfaces.—Motions.                      186

 _Third genus._—Diminution of the motions.—Direction in which they take
 place.                                                              187

 _Fourth genus._—Motions still less.                                 189

 _Fifth genus._—Remarkable obscurity of the motions.                 190


 III. _Observations upon the Immoveable Articulations._

 Situation, forms of each order.—Relation of the structure to the
 uses.                                                               191


 IV. _Of the means of Union between the Articular Surfaces._

 _Union of the immoveable Articulations._—Cartilages of union.       193

 _Union of moveable articulations._—Ligaments and muscles considered as
 articular bands.                                                    194


 ARTICLE FIFTH.

 DEVELOPMENT OF THE OSSEOUS SYSTEM.

 Remarks.                                                            195


 I. _State of the Osseous System during Growth._

 _Mucous State._—What should be understood by it.                    195

 _Cartilaginous State._—Period and mode of its development.—Of this
 state in the broad bones.                                           197

 _Osseous State._—Its phenomena.—Its period.                         198

 _Progress of the osseous state in the long bones_; 1st, in the middle;
 2d, in the extremities.                                             200

 _Progress of the osseous state in the broad bones._—Varieties
 according to the bones.—Formation of the ossa wormiana. _ib._

 _Progress of the osseous state in the short bones._                 202




 II. _State of the Osseous System after its Growth._

 Increase in thickness.—Composition and decomposition after the
 termination of growth in thickness.—Experiments.—State of the bones in
 old age.                                                            203


 III. _Peculiar Phenomena of the Development of the Callus._

 1st. Fleshy granulations.—2d. Adhesions of these granulations.—3d.
 Exhalation of gelatine and then of phosphate of lime.               206


 IV. _Peculiar Phenomena of the Development of the Teeth._

 _Organization of the teeth.—Hard portion of the
 teeth._—Enamel.—Experiment which distinguishes it from bone.—Its
 thickness.—Its nature.—Reflections upon its organization.—Osseous
 portion.—Its form.—Cavity of the tooth.                             209

 _Soft portion of the tooth._—Its spongy nature.—Its acute
 sensibility.—Remarks upon its different sympathies.                 211

 _First dentition considered before cutting._—Follicle.—Membrane of
 this follicle analogous to the serous membranes.—Albuminous nature
 of the fluid which lubricates it.—Mode of development of the osseous
 tooth upon the follicle.—Number of the first teeth.                 213

 _First dentition considered at the period of cutting._—Mode of
 cutting.—Accidents.—Their causes.                                   216

 _Second dentition considered before cutting._—Formation of the second
 follicle.                                                           217

 _Second dentition considered at the period of cutting._—Fall of the
 first teeth.—Appearance of the second.

 _Phenomena subsequent to the cutting of the second teeth._—Growth in
 length and thickness.—Fall of the teeth earlier than the death of the
 bones.—Why.—State of the jaws after the fall of the teeth.          219


 V. _Particular Phenomena of the Development of the Sesamoid Bones._

 _General arrangement of the sesamoid bones._—Situation.—Forms.      221

 _Fibro-cartilaginous state.—Osseous state._—Phenomena of the
 patella.—Use of the sesamoid bones.                                 222




 MEDULLARY SYSTEM.

 Division of this system.                                            225


 ARTICLE FIRST.

 MEDULLARY SYSTEM OF THE FLAT AND SHORT BONES, AND THE EXTREMITIES OF
 THE LONG ONES.


 I. _Origin and Conformation._

 It is an expansion of the vessels of the second order.              225


 II. _Organization._

 There is no medullary membrane.—Vascular interlacing.               226


 III. _Properties._

 There are only organic ones.—Experiments.                           227


 IV. _Development._

 There is no medullary oil in infancy.—Proofs.—Experiments.          227


 ARTICLE SECOND.

 MEDULLARY SYSTEM OF THE MIDDLE OF THE LONG BONES.


 I. _Conformation._

 It is like the cellular.                                            229


 II. _Organization._

 The medullary membrane is not an expansion of the periosteum.—Its
 vessels.                                                            230


 III. _Properties._

 Properties of texture.—Vital properties.—Animal sensibility.—Vitality
 more active than in the bones.                                      231




 IV. _Development._

 How the medullary membrane is formed.—The marrow of the infant is
 wholly different from that of the adult.—Proofs.                    233

 _Functions._—The marrow is exhaled.—Its alterations.—Its relations
 with the nutrition of the bone.—Necrosis.—The marrow is foreign to the
 synovia.                                                            234


 CARTILAGINOUS SYSTEM.

 What must be understood by cartilage.                               237


 ARTICLE FIRST.

 OF THE FORMS OF THE CARTILAGINOUS SYSTEM.


 I. _Forms of the Cartilages of the Moveable Articulations._

 Internal and external surfaces.—Relations of the two corresponding
 cartilages.—Peculiar characters of these cartilages in each kind of
 moveable articulations.                                             238


 II. _Forms of the Cartilages of the Immoveable Articulations._      241


 III. _Forms of the Cartilages of the Cavities._                     242


 ARTICLE SECOND.

 ORGANIZATION OF THE CARTILAGINOUS SYSTEM.


 I. _Texture peculiar to the Cartilaginous System._

 Fibres.—Remarkable resistance of the cartilaginous texture to
 putrefaction, maceration, &c.—Stewing and desiccation of this
 texture.—Its various alterations.                                   243




 II. _Parts common to the Organization of the Cartilaginous Texture._

 Cellular texture.—Means of seeing it.—Absence of blood vessels.—White
 vessels.—Their colour in jaundice.                                  245


 ARTICLE THIRD.

 PROPERTIES OF THE CARTILAGINOUS SYSTEM.


 I. _Physical Properties._

 Elasticity.—It appears to be owing to the superabundance of
 gelatine.—Proofs.                                                   247


 II. _Properties of Texture._

 They are very obscure.                                              248


 III. _Vital Properties._

 They are inconsiderable, as well as the sympathies.                 249

 _Character of the Vital Properties._—All the phenomena over which they
 preside have a chronic progress.—General observations upon the reunion
 of the parts.                                                       250


 ARTICLE FOURTH.

 DEVELOPMENT OF THE CARTILAGINOUS SYSTEM.


 I. _State of the Cartilaginous System in the First Age._

 Predominance of gelatine in the early periods.—Property which the
 cartilages then have of becoming red by maceration.—Vascular layers
 between the cartilage and the bone.—Cause which limits ossification in
 the cartilage.—Development of the cartilages of the cavities.       252


 II. _State of the Cartilaginous System in the after Ages._

 Different character which the gelatine assumes.—Ossification of the
 cartilages in old age.—Those of the cavities are the soonest
 ossified.                                                           255


 III. _Preternatural Development of the Cartilaginous System._

 Tendency of the membrane of the spleen to become the seat of
 it.—Preternatural cartilages of the articulations.                  257


 FIBROUS SYSTEM.


 GENERAL OBSERVATIONS.


 ARTICLE FIRST.

 OF THE FORMS AND DIVISIONS OF THE FIBROUS SYSTEM.

 The fibrous forms are either membranous or in fasciæ.               259


 I. _Of the Fibrous Organs of a Membranous Form._

 Fibrous membranes.—Fibrous capsules.—Fibrous sheaths.—Aponeuroses.   260


 II. _Of the Fibrous Organs in the form of Fasciæ._

 1st. Tendons.—2d. Ligaments.                                        262


 III. _Table of the Fibrous System._

 Analogy of the different organs of this system.—The periosteum is the
 common centre of these organs.                                      262


 ARTICLE SECOND.

 ORGANIZATION OF THE FIBROUS SYSTEM.


 I. _Of the Texture peculiar to the Organization of the Fibrous System._

 Peculiar nature of the fibrous texture.—Its extreme
 resistance.—Phenomena of this resistance.—It can be
 overcome.—Difference of the fibrous and muscular textures.—Experiments
 upon the fibrous texture subjected to maceration, ebullition,
 putrefaction, the action of the acids, the digestive juices, &c.    264


 II. _Of the Common Parts which enter into the Organization of the
 Fibrous System._

 Cellular texture.—Blood vessels.—Their varieties according to the
 organs.                                                             270


 ARTICLE THIRD.

 PROPERTIES OF THE FIBROUS SYSTEM.


 I. _Physical Properties._


 II. _Properties of Texture._

 Extensibility.—Peculiar law to which it is subjected there.
 Contractility.—It is almost nothing.—When it is manifested.         272


 III. _Vital Properties._

 Animal sensibility.—Singular mode of putting it in action by
 distension.—Consequence of this peculiar phenomenon to the fibrous
 texture.                                                            274

 _Character of the vital properties._—The vital activity is more
 evident in this system than in the preceding.—It appears that the
 fibrous texture does not suppurate.                                 277

 _Sympathies._—Examples of those of the animal and the organic
 properties.                                                         279


 ARTICLE FOURTH.

 DEVELOPMENT OF THE FIBROUS SYSTEM.


 I. _State of the Fibrous System in the First Age._

 The fibres are wanting in most of the fibrous organs of the
 fœtus.—Softness of these organs at this age.—Varieties of
 development.—Remarks upon rheumatism.                               281




 II. _State of the Fibrous System in the After Ages._

 Phenomena of the adult.—General stiffness in old age.               283


 III. _Preternatural Development of the Fibrous System._ Various
 tumours exhibit fibres analogous to those of this system.           284


 ARTICLE FIFTH.

 OF THE FIBROUS MEMBRANES IN GENERAL.


 I. _Forms of the Fibrous Membranes._

 Their double surface.—These membranes are like moulds of their
 respective organs.—Researches respecting that of the corpus
 cavernosum.—Experiments which show that it differs essentially from
 the subjacent spongy texture.—Other researches upon that of the
 testicle.                                                           285


 II. _Organization of the Fibrous Membranes._                        288


 III. _Of the Periosteum. Of its Form._

 Its two surfaces.—Their adhesion to the bones.                      289

 _Organization of the periosteum._—Preternatural development of its
 fibres in elephantiasis.—Its connexions with the fibrous bodies in
 infancy.                                                            291

 _Development of the periosteum._

 _Functions of the Periosteum._—In what way it assists ossification.—It
 relates as much to the fibrous organs as to the bones.              292


 IV. _Perichondrium._

 Experiments upon this membrane.                                     294


 ARTICLE SIXTH.

 OF THE FIBROUS CAPSULES.


 I. _Forms of the Fibrous Capsules._

 They are very few.—Arrangement of the two principal ones.—Canal
 between them and the synovial capsule.                              295


 II. _Functions of the Fibrous Capsules._                            296




 ARTICLE SEVENTH.

 OF THE FIBROUS SHEATHS.

 Their division.                                                     297


 I. _Partial Fibrous Sheaths._

 Their form.—Their arrangement.—Why the flexor tendons are alone
 provided with them.                                                 297


 II. _General Fibrous Sheaths._                                      299


 ARTICLE EIGHTH.

 OF THE APONEUROSES.


 I. _Of the Aponeuroses for Covering._

 Their division.                                                     299

 _Aponeuroses for general covering._                                 300

 _Forms._—They are accommodated to the extremities, &c. _ib._

 _Tensor muscles.—Organization._—Examples of the tensor muscles.—Their
 uses relative to the aponeuroses.—Analogy with the tendons and
 difference from them.—Arrangement of the fibres.                    301

 _Functions._                                                        302

 _Aponeuroses for partial covering._—Examples.—General uses of these
 aponeuroses.                                                        303


 II. _Of the Aponeuroses of Insertion._

 _Aponeuroses of insertion with a broad surface._—Their
 origin.—Their uses.—The identity of their nature with that of the
 tendons.—Experiments.                                               304

 _Aponeuroses of insertion in the form of an arch._—They are rare.—They
 exist where vessels pass through.—They do not compress them.        305

 _Aponeuroses of insertion with separate fibres._                    306




 ARTICLE NINTH.

 OF THE TENDONS.


 I. _Form of the Tendons._

 Relation of the uses with the forms.—Union with the fleshy fibres.   307


 II. _Organization of the Tendons._

 Method of seeing their fibres advantageously.—They appear to be
 destitute of blood vessels.—Their tendency to be penetrated with the
 phosphate of lime.                                                  309


 ARTICLE TENTH.

 OF THE LIGAMENTS.


 I. _Ligaments with, Regular Fasciæ._

 General arrangement.                                                311


 II. _Ligaments with Irregular Fasciæ._                              312


 FIBRO-CARTILAGINOUS SYSTEM.

 Organs which compose it.                                            315


 ARTICLE FIRST.

 OF THE FORMS OF THE FIBRO-CARTILAGINOUS SYSTEM.

 Division into three classes of the organs of this system.—Characters
 of each class.                                                      315




 ARTICLE SECOND.

 ORGANIZATION OF THE FIBRO-CARTILAGINOUS SYSTEM.


 I. _Texture peculiar to the Organization of the Fibro-Cartilaginous
 System._

 It arises, 1st, from a fibrous substance; 2d, from a cartilaginous
 one.—It owes its resistance to the first and its elasticity to the
 second.—Action of caloric, air and water upon the fibro-cartilaginous
 texture.—It reddens by maceration.—Absence of the perichondrium upon
 most of the fibro-cartilages.                                       317


 II. _Parts common to the Organization of the Fibro-Cartilaginous
 System._                                                            320


 ARTICLE THIRD.

 PROPERTIES OF THE FIBRO-CARTILAGINOUS SYSTEM.


 I. _Physical Properties._

 Elasticity and suppleness united.                                   320


 II. _Properties of Texture._

 Extensibility.—It is quite evident in it.—Contractility.—Difference
 from elasticity.                                                    321


 III. _Vital Properties._

 They are inconsiderable.—Influence of the obscurity of these forces
 upon the properties of the fibro-cartilages.                        322


 ARTICLE FOURTH.

 DEVELOPMENT OF THE FIBRO-CARTILAGINOUS SYSTEM.


 I. _State of this System in the First Age._

 Mode of development of the three classes.                           323




 II. _State of this System in the after Ages._

 General rigidity of these organs.—Consequences.—Ossification of the
 fibro-cartilages rare.                                              325


 MUSCULAR SYSTEM OF ANIMAL LIFE.

 Difference between the muscles of the two lives.—Observations upon
 those of animal life.                                               327


 ARTICLE FIRST.

 OF THE FORMS OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.

 Division of these muscles into long, broad and short.               327


 I. _Forms of the Long Muscles._

 Place which they occupy.—Their division.—Their separation and
 reunion.—Peculiar forms of the long muscles of the spine.           328


 II. _Forms of the Broad Muscles._

 Where they are situated.—Thickness.—Peculiar forms of the broad
 pectoral muscles.                                                   330


 III. _Forms of the Short Muscles._

 Where they are found.—Their arrangement.—Remarks upon the three
 species of muscles.                                                 331


 ARTICLE SECOND.

 ORGANIZATION OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.


 I. _Texture peculiar to this Organization._

 Arrangement of this texture into fasciculi.—Its division into
 fibres.—Length of the fleshy fibres compared with that of the
 muscle.—Their direction.—Their figure.—Their softness.—Ease of their
 rupture in the dead body.—Difficulty in the living.                 332

 _Composition of the muscular texture._—Action of the air in
 desiccation and putrefaction.—Action of cold water.—Maceration and its
 products.—Ease with which the colouring substance is removed.—Analogy
 of the remaining texture with the fibrin of the blood.—Relation
 of the forces with this texture.—Action of boiling water.—Some
 peculiar phenomena of common boiled flesh.—Roasting of the fleshy
 texture.—Singular affinity of the digestive juices to this sort of
 texture.—General observations.—Influence of sex and the genital organs
 upon the fleshy texture.                                            336


 II. _Parts common to the Organization of this System._

 _Cellular texture._—Manner in which it envelops the fibres.—Its uses
 for muscular motion.—Experiment.—Fatty muscles.                     343

 _Blood vessels._—Arteries.—Of the blood of the muscles.—Of
 their colour.—Free and combined state of the colouring
 substance.—Veins.—Remarks upon the injection of them.               346

 _Nerves._—There are hardly any but those of animal life.—Their
 difference in the extensors and the flexors.—Manner in which the
 nerves penetrate the muscles.                                       348


 ARTICLE THIRD.

 PROPERTIES OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.


 I. _Properties of Texture. Extensibility._

 This property is continually in action.—It is in proportion to the
 length of the fibres.—Its exercise in diseases.                     350

 _Contractility of texture._—Phenomena of the antagonists.—Distinction
 in these phenomena of that which belongs to the vital properties
 from that which belongs to those of texture.—Of the contractility of
 texture in diseases.—Extent and quickness of the contractions.—They
 continue after death.—Essential differences between the contractility
 of texture and horny hardening. Their parallel.                     352




 II. _Vital Properties._

 _Properties of animal life.—Sensibility._—Most of the ordinary agents
 do not develop it.—It is put into action by repeated contractions.—Of
 the sensation of lassitude.—Sensibility of the muscles in their
 affections.                                                         359

 _Animal Contractility._—It should be considered in three relations. 361

 _Animal contractility considered in the brain._—The principle of this
 property exists in this organ.—Proofs drawn from observation.—Proofs
 derived from diseases.—Proofs borrowed from experiments upon
 animals.—Cases in which the brain is foreign to the muscles.        362

 _Animal contractility considered in the nerves._—Influence
 of the spinal marrow upon this property.—Observations and
 experiments.—Influence of the nerves.—Observations and
 experiments.—All the nerves do not transmit equally the different
 irradiations of the brain.—Direction of the propagation of the nervous
 influence.                                                          367

 _Animal contractility considered in the muscles._—Necessary conditions
 in the muscle for it to contract.—Obstacles to contraction.—Various
 experiments.                                                        374

 _Causes which bring into action animal contractility._—Division
 of these causes.—Of the will.—Of the involuntary causes.—Direct
 excitement.—Sympathetic excitement.—Influence of the passions.—Remarks
 upon the motion of the fœtus.                                       374

 _Duration of the animal contractility after death._—Various
 experiments.—Consequences relative to respiration.—Variety of the
 duration of this property.—How it is extinguished.                  379

 _Organic Properties._—Organic sensibility and insensible organic
 contractility.—Sensible organic contractility.—Various experiments
 upon this last property.—Phenomena of irritations.—In order to study
 this contractility the animal contractility must be destroyed.—How
 this is done.—Various modes of contraction.                         382

 _Sympathies._—The animal sensibility is the property especially
 brought into action by them.—General Remarks.—Sympathies of animal
 sensibility.—The organic properties are rarely brought into action. 386

 _Characters of the vital properties._—Different remarks upon these
 characters.                                                         388




 ARTICLE FOURTH.

 PHENOMENA OF THE ACTION OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.


 I. _Force of the Muscular Contraction._

 Difference according as it is put into action by stimuli or by the
 cerebral influence.—Experiments.—Influence of muscular organization
 upon contraction.—The laws of nature the reverse of those of mechanics
 in the production of motions.—Multiplication of forces.—Uncertainty of
 calculations upon this point.                                       390


 II. _Quickness of the Contractions._

 Varieties according as the contractions are, 1st, from stimuli; 2d,
 from nervous action.—Different degrees of quickness in different
 individuals.—Influence of habit upon this degree.                   395


 III. _Duration of the Contractions._                                397


 IV. _State of the Muscles in Contraction._

 Different phenomena which they then experience.—Essential remark upon
 the different modes of contraction.                                 398


 V. _Motions imparted by the Muscles._

 _Simple Motions._—1st. In the muscles with a straight direction.—How
 we determine the uses of these muscles.—2d. In the muscles with a
 reflected direction.—3d. In those with a circular direction.        400

 _Compound Motions._—Almost every motion is compound.—How.—Different
 examples of compound motions.—Antagonist muscles.                   403


 VI. _Phenomena of the Relaxation of the Muscles._

 They are opposite to the preceding.                                 406




 ARTICLE FIFTH.

 DEVELOPMENT OF THE MUSCULAR SYSTEM OF ANIMAL LIFE.


 I. _State of this System in the Fœtus._

 It contains but little blood.—Slight contractility at this
 age.—Influence upon these phenomena, of the blood which then
 penetrates the muscles.—These organs are then slender and weak.     407


 II. _State of this System during Growth._

 Sudden effect of the red blood which penetrates the muscles, and of
 the other irritations which are connected with it.—Colour of the
 Muscles.—Period of the brightest colour.—Varieties of the action of
 reagents on the fleshy texture of young animals.                    410


 III. _State of this System after Growth._

 The thickness constantly increases.—The external forms are more
 evident.—Colour in the adult.—Innumerable variety.                  413


 IV. _State of this System in Old Age._

 Increase of density.—Diminution of cohesion.—Phenomena of the
 vacillation of the muscles.—Atrophous muscles.                      416


 V. _State of the System at Death._

 Relaxation or stiffness of the muscles.                             419


 END OF CONTENTS TO VOL. II.




 VOLUME THIRD.

 MUSCULAR SYSTEM OF ORGANIC LIFE.


 GENERAL OBSERVATIONS.


 ARTICLE FIRST.

 FORMS OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

 PAGE

 Curved direction of the fibres.—They do not arise from the fibrous
 system.—Varieties of the muscular forms, according to the organs.     4


 ARTICLE SECOND.

 ORGANIZATION OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

 General difference of organization from the preceding muscles.        5


 I. _Peculiar Texture._

 General arrangement of the muscular fibre.—Analogy with the preceding
 and difference.                                                       6


 II. _Common Parts._

 Cellular Texture.—Blood vessels.—Nerves of the ganglions and of the
 brain.—Proportion of each class.                                      8




 ARTICLE THIRD.

 PROPERTIES OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.


 I. _Properties of Texture._

 _Extensibility._—Particular character of this property in the organic
 muscles.—In aneurisms of the heart and in pregnancy, it is not the
 extensibility that is brought into action.—Remarks upon this
 subject.                                                             10

 _Contractility._—It is in proportion to extensibility.—The substances
 contained in the hollow muscles are their antagonists.—Remarks.      14


 II. _Vital Properties._

 _Sensibility._—Of the lassitude of the organic muscles.—Remarks upon
 hunger.                                                              15

 _Animal Contractility._—It is nothing in these muscles.—Different,
 experiments.—Observations.—Of the muscles in part voluntary and
 in part organic.—Experiments.—Remarks upon the bladder, rectum,
 &c.—Absence of the nervous influence upon the organic muscles.       17

 _Organic Properties._—General Remarks.                               24

 _Of sensible organic contractility considered under the relation of
 the stimuli._                                                        25

 _Natural stimuli._—Different observations.—Remarks upon the fluids and
 solids.—Influence of the quality and quantity of the fluids upon the
 hollow muscles. _ib._

 _Artificial stimuli._—Action of these stimuli.—Different modes of
 action.—Limits of the horny hardening and vital contraction.         28

 _Of sensible organic contractility, considered in relation to the
 organs._                                                             31

 _First variety. Diversity of the muscular texture._—Each muscle is
 particularly in relation with some determinate substance.—Application
 of this principle to the natural and foreign fluids. _ib._

 _Second variety. Age._—Vivacity of the contractility in
 infancy.—Consequences.—Opposite phenomenon in old age.               33

 _Third Variety. Temperament._—Difference of individuals in regard to
 organic muscular force.—This force is not always in relation to the
 animal muscular force.—It cannot be increased like it by habit.      34

 _Fourth Variety. Sex._                                               35

 _Fifth Variety. Season and climate._                                 36

 _Sensible organic contractility considered in relation to the
 action of stimulants upon the organs._—The constant existence of an
 intermediate organ for this action.—Nature of this intermediate organ.
 _ib._

 _Sensible organic contractility considered in relation to its duration
 after death._—Difference of this duration according to the kind of
 death.—Remarks.                                                      38

 _Sympathies._—Sympathies of the heart.—Sympathies of
 the stomach.—Remarks upon bilious vomitings.—General
 observations.—Sympathies of the intestines, the bladder, &c.         40

 _Character of the vital properties._—Vital energy very considerable in
 this system.—Its affections act upon its predominant vital force.—The
 infrequency of the affections which suppose a derangement of the
 organic properties.                                                  44


 ARTICLE FOURTH.

 PHENOMENA OF THE ACTION OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.


 I. _Force of Contractions._

 Difference from the force of contraction of the preceding system.—It
 is greater in the vital phenomena than in experiments.—Inaccuracy of
 calculations.                                                        46


 II. _Quickness of the Contractions._

 In experiments.—During life.—Comparison with the quickness of the
 preceding muscles.                                                   49


 III. _Duration of the Contractions._                                 50


 IV. _State of the Muscles in Contraction._

 Difference in this respect between the heart and the gastric muscles.
 _ib._


 V. _Motions imparted by the Organic Muscles._                        51


 VI. _Phenomena of the Relaxation of the Organic Muscles._

 Differences of this relaxation from the active dilatation of the
 muscles.—Proofs of the phenomena of this dilatation.                 52




 ARTICLE FIFTH.

 DEVELOPMENT OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.


 I. _State of this System in the Fœtus._

 Predominance of the heart.—State of the other muscles.—Weakness of the
 organic contractility at this age.                                   55


 II. _State of the Organic Muscular System during Growth._

 General increase of action at birth.—Of the growth in thickness and of
 that in length.—Their differences.                                   58


 III. _State of the Organic Muscular System after Growth._            61


 IV. _State of the Organic Muscular System in Old Age._

 This system outlives, if we may so say, the preceding.—Phenomenon
 resulting from its weakness.                                         62


 MUCOUS SYSTEM.


 ARTICLE FIRST.

 OF THE DIVISIONS AND FORMS OF THE MUCOUS SYSTEM.


 I. _Of the two general Mucous Membranes, the Gastro-pulmonary and the
 Genito-urinary._

 Difference of these two membranes.—Their relation.                   66


 II. _Adhering Surface of the Mucous Membranes._

 Its relations.—It is everywhere subjacent to the muscles.—Sub-mucous
 texture.—Experiments.                                                69


 III. _Free surface of the Mucous Membranes._

 Of the folds it exhibits.—1st. Of those which comprehend all the
 membranes.—2d. Of those which are permanent upon the mucous
 surface.—3d. Of those which are owing to a state of vacuity of the
 hollow organs.—Different experiments.—The extent of the mucous
 surfaces is always nearly the same, whatever may be the state of their
 organs.—Relation of their free surface with external bodies.—Their
 sensibility is accommodated to this relation.—The term _foreign body_
 is merely comparative.                                               70


 ARTICLE SECOND.

 ORGANIZATION OF THE MUCOUS SYSTEM.


 I. _Texture peculiar to this Organization._

 What it presents for consideration.

 _Mucous Corion._—Its variable thickness.—Mucous nature of the
 membrane of the ear.—Pathological consequences.—Softness of the
 mucous texture.—Action of the air, water, caloric, the acids and the
 digestive juices upon the mucous texture.                            76

 _Mucous papillæ._—Their varieties of form.—Their nervous
 nature.—Proofs of this nervous nature.—Their influence upon the
 sensibility of the mucous organs.                                    83


 II. _Common Parts._

 _Of the mucous glands and the fluids which they
 secrete._—Situation.—Forms.—Size.—Texture.                           86

 _Mucous fluids._—Physical properties.—Action of different agents upon
 them.—Their functions.—Parts in which they are most abundant and
 those in which they are less so.—Susceptibility of being increased
 by any irritation made upon their excretories.—Consequences.—Remarks
 upon the excitement of the mucous surfaces in diseases.—Uses of the
 mucous membranes in relation to the habitual evacuation of their
 fluids.—General remarks upon the secreted fluids.—Singular sensation
 arising from the continuance of the mucous fluids upon their
 respective surfaces.                                                 88

 _Blood vessels._—Their varieties of proportion.—Their superficial
 position.—Consequence.—Redness of the mucous system.—It often loses
 it.—Experiments upon the state of the mucous vessels in the fulness
 and vacuity of their hollow organs.—Other experiments upon the
 influence of the gases upon the colour of the mucous system.—Causes of
 its redness.—Colouring substance combined and free.                  96

 _Exhalants._—Is there exhalation upon the mucous system?—Pulmonary
 exhalation.—A great part of the pulmonary perspiration arises from the
 solution of the mucous juices.—Other mucous
 exhalations.—Hemorrhages.                                           105

 _Absorbents._—Proofs of the mucous absorption.—Irregularity of this
 absorption.—Cause of this irregularity.                             107

 _Nerves._—Those of the brain.—Those of the ganglions.—Their respective
 distribution upon this system.                                      108


 ARTICLE THIRD.

 PROPERTIES OF THE MUCOUS SYSTEM.


 I. _Properties of Texture._

 They are less than they at first seem to be.—They are however
 real.—Their variety.—The mucous ducts are not obliterated by the
 contractility of texture when they are empty.                       109


 II. _Vital properties._

 _Properties of animal life._—Acute sensibility of the mucous
 system.—Influence of habit upon this property.—Consequences of this
 remark.—Mucous sensibility in inflammations.                        111

 _Properties of organic life._—Organic sensibility and insensible
 contractility are very evident here.—Why.—Consequences as it respects
 diseases.—Varieties of these properties.-Species of sensible organic
 contractility in the mucous texture.                                114

 _Sympathies._—How we shall divide them.                             117

 _Active Sympathies._—Example of these sympathies for each vital
 property.                                                           118

 _Passive Sympathies._—The predominant ones are those of insensible
 organic contractility.—Why.                                         120

 _Character of the vital properties._—Vital activity of this
 system.—Its varieties.—Consequences as it regards diseases.—Remarks
 upon the stomachic sympathies.                                      123




 ARTICLE FOURTH.

 DEVELOPMENT OF THE MUCOUS SYSTEM.


 I. _State of the Mucous System in the First Age._

 It follows the state of the organs to which it belongs.—Delicacy of
 the papillæ.—The mucous redness is then deeper.—Sudden change at
 birth.—Why.—Phenomenon of puberty.                                  125


 II. _State of the Mucous System in the After Ages._

 Its phenomena in the adult.—Its phenomena in old age.               129


 SEROUS SYSTEM.


 GENERAL OBSERVATIONS.


 ARTICLE FIRST.

 OF THE EXTENT, FORMS AND FLUIDS OF THE SEROUS SYSTEM.

 General arrangement of its membranes.—Of the serous surface considered
 in general.—Every serous membrane is a sac without an opening.      131


 I. _Free Surface of the Serous Membranes._

 It is smooth and polished.—This attribute is foreign to
 compression.—This surface insulates the organs to which the
 serous surfaces belong.—Its influence upon the motion of these
 organs.—Adhesions of the serous surfaces.—Their division.           134


 II. _Adhering Surface of the Serous System._

 Means of union.—The serous membranes often change relations with their
 organs.—This is owing to the laxity of the adhesions.—Adhesions more
 close.                                                              140




 III. _Serous Fluids._

 Their quantity.—Varieties of this quantity.—Experiments.—Morbid
 varieties.—Nature of these fluids.                                  142


 ARTICLE SECOND.

 ORGANIZATION OF THE SEROUS SYSTEM.

 The serous membranes have but one layer.—Its colour.—Its thickness. 144


 I. _Cellular nature of the Serous Texture._

 Proofs of this cellular nature.—Experiments by maceration, ebullition,
 desiccation, stewing and putrefaction.—Differences between the
 cellular and serous textures.                                       145

 II. _Parts common to the organization of the Serous System._

 _Exhalants._—Various proofs of serous exhalation.                   149

 _Absorbents._—Proofs of serous absorption.—Experiments.—Mode of origin
 of the absorbents.                                                  150

 _Blood vessels._—The serous membranes have but very few of them.—Those
 which are subjacent do not belong to them.—Proofs.                  151


 III. _Varieties of Organization of the Serous System._

 Different examples of these varieties.—Consequences in regard to
 diseases.—Remarks upon the pericardium.—Common characters.          153


 ARTICLE THIRD.

 PROPERTIES OF THE SEROUS SYSTEM.


 I. _Properties of Texture._

 _Extensibility._—It is less than it at first seems to be.—Why.—Use of
 the folds of the serous membranes.—Of their displacement.—Pain from
 these displacements in inflammation.                                155

 _Contractility._—Less than it appears to be.—It is however real.    156


 II. _Vital Properties._

 They enjoy but little animal sensibility.—Why.—Experiments.—The
 organic properties are very sensible.—Consequences.                 157

 _Sympathies._—Various examples.—Remarks upon sympathetic
 exhalations.—Remark upon the serum of dead bodies.                  158


 ARTICLE FOURTH.

 DEVELOPMENT OF THE SEROUS SYSTEM.


 I. _State of this System in the First Age._

 Extreme tenuity of the surfaces.—Quantity of the
 fluids.—Quality.—Changes at birth.—Experiments.                     161


 II. _State of the Serous System in the After Ages._

 The serous surfaces obey the laws of their respective
 organs.—Increased density in old age.—Ossification rare.            162


 III. _Preternatural Development of the Serous System._

 Various observations.                                               164


 SYNOVIAL SYSTEM.

 Points of resemblance between this system and the preceding.—Its
 division.                                                           165




 ARTICLE FIRST.

 ARTICULAR SYNOVIAL SYSTEM.


 I. _How the Synovia is separated from the mass of blood._

 There are three ways in which fluids may be separated from the blood.

 _Is the Synovia transmitted by secretion to the articular
 surfaces?_—Negative proofs.—Of the pretended synovial
 glands.—Experiments.

 _Is the Synovia transmitted by transudation to the articular
 surfaces_?—Negative proofs.—Another opinion.

 _Is the Synovia transmitted by exhalation to the articular
 surfaces?_—Positive proofs.—Analogy between the exhaled fluids and the
 synovia.—Consequences.                                              167


 II. _Remarks upon the Synovia._

 Its quantity.—It varies a little.—Rare alterations of this fluid.—Its
 difference from the serous fluids.                                  173


 III. _Of the Synovial Membranes._

 _Forms._—They represent sacs without an opening.—Difference from the
 fibrous capsules.—These capsules are wanting in the greatest number of
 articulations.—Experiments.—Proofs of the synovial membrane where it
 adheres.                                                            175

 _Organization._—Analogy with the serous surfaces.—Structure of the
 pretended synovial glands.                                          180

 _Properties._—Properties of texture.—Vital
 properties.—Experiments.—The synovial system is foreign to most
 diseases.                                                           182

 _Functions._—They are foreign to the solidity of the
 articulation.—They have relation only to the synovia.               183

 _Natural Development._—State of the synovial membrane in infancy,
 adult and old age.                                                  184

 _Preternatural Development._—Remarks upon this development.         185


 ARTICLE SECOND.

 SYNOVIAL SYSTEM OF THE TENDONS.

 It is often confounded with the preceding.                          186

 _Forms; relations; synovial fluid._—Forms of sacs without
 an opening.—Varieties of these forms.—Smooth and adhering
 surface.—Relation with the tendon.—Preternatural increase of the
 fluid.                                                              186

 _Organization, properties, development._—Their phenomena are analogous
 to those of the preceding system.—Remarks upon the affections of this
 kind of synovial membranes.                                         189


 GLANDULAR SYSTEM.

 General observations.—What a gland is.                              193


 ARTICLE FIRST.

 SITUATION, FORMS, DIVISION, &C. OF THE GLANDULAR SYSTEM.

 Sub-cutaneous and deep position.—Relation of the position of
 the glands with their excretion.—Varieties of the glandular
 forms.—Distinction of these varieties.—External surface of the
 glands.                                                             194


 ARTICLE SECOND.

 ORGANIZATION OF THE GLANDULAR SYSTEM.


 I. _Texture peculiar to the Organization of this System._

 The fibrous arrangement is foreign to the glands.—There is but little
 resistance in the glandular texture.—Triple arrangement of this
 texture.—Uncertainty of the researches upon its nature.—Different
 experiments upon this texture.—Desiccation.—Peculiar effect of
 stewing.—Roasting.—Maceration.—Action of the acids, gastric
 juice, &c.                                                          198

 _Of the excretories, their origin, divisions, &c. of the glandular
 reservoirs._—Origin.—Course.—Division of the glands into three
 classes, in regard to the termination of their excretories.—Of the
 reservoirs.—What supplies their place when they are wanting.—Motion of
 the fluids in the excretories.                                      204

 _Size, direction and termination of the excretories._—All the
 excretories open upon the mucous or cutaneous systems.—Observations
 upon the intestinal canal.                                          206

 _Remarks upon the secreted fluids._—They can re-enter the
 circulation.—Various experiments on this subject.—Consequences.     208

 _Structure of the excretories._—Internal membrane.—External
 texture.                                                            213


 II. _Parts common to the Organization of the Glandular System._

 _Cellular Texture._—Division of the glands into two classes, in regard
 to this texture.—Serum and fat of this texture.—Fatty livers.       214

 _Blood vessels._—Different ways in which they enter the glands,
 according as they are or are not surrounded with membranes.—Course
 of the arteries in the glands.—Veins.—They pour their blood into the
 general black blood.—Reflux from the heart to the glands.           216

 _Of the blood of the glands._—Division of the glands into three
 classes, as it regards the fluid which penetrates them.—Great quantity
 of blood contained in the liver and the kidney.—Variety as it respects
 secretion.                                                          219

 _Nerves._—Of those of the ganglions and of the cerebral ones.—Their
 proportion.—How they enter the glands.—Secretion is independent of
 nervous influence.                                                  221

 _Exhalants and absorbents._                                         223


 ARTICLE THIRD.

 PROPERTIES OF THE GLANDULAR SYSTEM.


 I. _Properties of Texture._

 They are inconsiderable.—Proofs.—New remarks upon the reflux of the
 black blood in the glands.                                          224


 II. _Vital Properties._

 _Properties of animal life._—Experiments upon animal
 sensibility.—Varieties of the results.                              226


 _Properties of organic life._—The insensible contractility and the
 corresponding sensibility are the predominant ones.—Their influence
 upon secretion.—Varieties of the secreted fluids.—Organic affections
 of the glands.—Remarks.                                             227

 _Sympathies._                                                       230

 _Passive sympathies._—Various examples.—Sympathies the causes of which
 act at the extremity of the excretories.—Influence of the passive
 sympathies of the glands in diseases.—Remark upon that of each gland.

 _Active Sympathies._—Various remarks.

 _Characters of the vital properties._                               235

 _First character.—Life peculiar to each gland._—Proofs of this
 peculiar life.—Of its influence in a state of health and disease.

 _Second character.—Remission of the glandular life._—The glands have a
 species of sleep.—Various examples.                                 238

 _Third character.—The glandular life is never simultaneously raised
 in the whole system._—Application of this remark to the digestive
 order.—Advantage of the artificial excitement of the glands in
 diseases.                                                           239

 _Fourth character.—Influence of climate and season upon the glandular
 life._—The sweat and many secreted fluids are opposite to each other
 in this respect.                                                    241

 _Fifth character.—Influence of sex upon the glandular life._        242


 ARTICLE FOURTH.

 DEVELOPMENT OF THE GLANDULAR SYSTEM.


 I. _State of this System in the Fœtus._

 The glands are very conspicuous at this age.—Yet the secretions are
 not great.                                                          243


 II. _State of this System during Growth._

 Suddenly increased activity at birth.—Yet it is not the glandular
 system which predominates in the first age.—Remarks upon its
 diseases.—The mucous and lachrymal glands are the most frequently in
 action in infancy.                                                  244




 III. _State of this System after Growth._

 Period of puberty.—Its influence upon the glands.—Influence of the
 glands of digestion at the adult age.                               247


 IV. _State of this System in old Age._

 Of the change in the texture of the glands from the effect of
 age.—Many glands still secrete much fluid in old age.—Relation of this
 phenomenon with nutrition.                                          249


 DERMOID SYSTEM.


 GENERAL OBSERVATIONS.


 ARTICLE FIRST.

 FORMS OF THE DERMOID SYSTEM.


 I. _External Surface of the Dermoid System._

 Various folds of this surface.—Their different nature.              254


 II. _Internal Surface of the Dermoid System._

 Its relations.—Absence of the fleshy pannicle in man.—Consequences. 256


 ARTICLE SECOND.

 ORGANIZATION OF THE DERMOID SYSTEM.


 I. _Texture peculiar to the Organization._

 _Chorion._—Its thickness in the different regions.—Its
 structure.—Method of seeing it.—Variety of this structure according
 to the regions.—Small spaces of the chorion.—Fibres.—Their nature.—It
 approximates that of the fibrous texture.—Yet it differs from it.—The
 chorion is foreign to the functions of the skin relative to animal and
 organic life.                                                       258

 _Of the reticular body._—Idea that has been formed of it.—What
 it is.—Vascular net-work.—Colouring substance.—Analogy among the
 diversity of races.—How this diversity should be considered.—Of the
 cases in which the blood enters the reticular body.—Singular property
 of the vessels of the face of receiving more than the others.—Cause of
 this phenomenon.—Triple means of expression of the passions.—Relation
 between the tendency of the facial capillary system to receive blood
 and diseases.—Double state of the reticular body.—Phenomena at the
 instant of death.—Experiments.                                      266

 _Papillæ._—Situations.—The cutaneous prominences must not be taken
 for them.—Experiments to prove the nature of these prominences.—Their
 varieties.—Forms and nervous structure of the papillæ.              273

 _Action of different bodies upon the dermoid texture._              276

 _Action of light._—Men whiten like plants.—Examples. _ib._

 _Action of caloric._—Effects which it produces on the skin during life
 according to its different degrees.—Effect of cold.—General remarks
 upon gangrene and antiseptics.—False opinions of authors.           277

 _Action of the air._—Remarks upon the influence of this fluid upon
 the evaporation of the transpiration.—It is foreign to this function
 itself.—Desiccation of the skin by the air.—Its putrefaction.       282

 _Action of water._—General uses of baths.—Their use is
 natural.—Maceration of the skin.—Pulpy state.—Stewing of the
 skin.—Mode of horny hardening.—Vesicles that arise the instant it
 takes place.—Other phenomena of stewing.                            285

 _Action of the acids, alkalies, and other substances._—Various
 experiments with reagents.—Remarks.                                 290


 II. _Parts common to the Organization of the Dermoid System._

 _Cellular texture._—Manner in which it is distributed.—Remarks upon
 biles.—Sometimes it is wholly destroyed.—Appearance which the skin
 then has.—Remarks upon leucophlegmasia.                             291

 _Blood vessels._—Manner in which they are distributed.—Dilatation of
 the veins in some cases.                                            293

 _Nerves._—Mode of their distribution.                               294


 _Absorbents._—Proofs of cutaneous absorption.—Absorption of
 virus.—Table of this absorption.—Varieties it experiences.—Absorption
 of medicines.—Experiments.—Character of irregularity of the cutaneous
 absorptions.—To what this character is owing.—Influence of weakness on
 this absorption.                                                    294

 _Exhalants._—Mode of distribution.—Cutaneous exhalations.—Uncertainty
 of calculations upon this point.—Relation of this exhalation with the
 secretions.—Relation with the pulmonary exhalation.—Experiment upon
 this last exhalation.—Remarks upon the causes of many coughs.—Defect
 of evaporation of the fluid deposited upon the bronchia.—The cutaneous
 exhalants vary.—Are they under the nervous influence?—This does not
 appear probable.                                                    299

 _Sebaceous Glands._—Oily fluid of the skin.—Its quantity.—Its
 varieties.—Its sources.—We have but few data as it regards the
 sebaceous glands.                                                   305


 ARTICLE THIRD.

 PROPERTIES OF THE DERMOID SYSTEM.


 I. _Properties of Texture._

 They are very evident.—They are often less than they seem to
 be.—Phenomena of extensibility and contractility.                   308

 II. _Vital Properties._

 _Properties of animal life._—Sensibility.—Of the feeling.—Of the
 touch.—Its characters.—Its differences from the other senses.—Seat of
 cutaneous sensibility.—The mode.—Pain peculiar to the skin.—Influence
 of habit upon this sensibility.—Various reflections.—Diminution of the
 cutaneous sensibility.                                              311

 _Properties of organic life._—They are especially organic
 sensibility and insensible contractility.—Phenomena over which they
 preside.—Division of cutaneous diseases.—Excitants of the cutaneous
 organic sensibility.—Sensible organic contractility is but slightly
 apparent.                                                           318

 _Sympathies.—Passive Sympathies._—Different examples and remarks upon
 the sympathies of heat.—General remarks upon the sensations of heat
 and cold.—Influence of sympathies upon the sweat.                   322

 _Active Sympathies._—These sympathies are relative to each of the
 classes of diseases pointed out above.—Various examples.—General
 remarks.                                                            326

 _Characters of the vital properties.—First character.—The
 cutaneous life varies in each region._—Varieties of animal
 sensibility.—Varieties in the organic properties.                   331

 _Second character.—Intermission in one relation, continuity in
 another._—The peculiar life of the skin is intermittent as it respects
 the functions of relation.—Its continuity as it respects its organic
 functions.                                                          332

 _Third character.—Influence of sex._                                333

 _Fourth character.—Influence of temperament._                       334


 ARTICLE FOURTH.

 DEVELOPMENT OF THE DERMOID SYSTEM.

 I. _State of this System in the Fœtus._

 A gluey covering in the first periods.—Absence of certain wrinkles in
 the fœtus.—Laxity of adhesion.—State of the vital properties of the
 skin of the fœtus.—Its functions at this age.                       335

 II. _State of this System during Growth._

 Sudden revolution at birth.—Entrance of the red blood into the
 skin.—Consequences.—State of the cutaneous vital forces in
 infancy.—State of the cutaneous texture.                            337

 III. _State of the Dermoid System after Growth._

 Increasing proportion of the fibrous substance, and decreasing
 proportion of the gelatinous.—Remark upon the diseases and affections
 of the skin.                                                        341


 IV. _State of the Dermoid System in Old Age._

 State of the cutaneous texture.—Phenomena which arise from it.—State
 of the vital forces.—State of the functions.                        344




 EPIDERMOID SYSTEM.

 General Observations.—Division.                                     349


 ARTICLE FIRST.

 OF THE EXTERNAL EPIDERMIS.


 I. _Forms, Relations with the Dermis, &c._

 Wrinkles.—Pores.—Adhesion to the skin.—Means of destroying this
 adhesion.—Arrangement.                                              350


 II. _Organization, Composition, &c._

 Uniform thickness in most parts.—Remarkable thickness on the foot and
 the hand.—Consequences of this thickness.—Experiments upon the colour
 of negroes.—Epidermoid texture.—Its peculiar nature.—Action of the
 air, water, caloric, the acids, the alkalies, &c. upon the epidermoid
 texture.                                                            353


 III. _Properties._

 Extensibility.—The animal properties are foreign to the epidermis.—It
 appears to be destitute also of organic properties.—Continual
 destruction of the epidermis.—Its reproduction when it is removed.  360


 IV. _Development._

 State of the epidermis in the fœtus, the adult and the old person.   364


 ARTICLE SECOND.

 INTERNAL EPIDERMIS. GENERAL OBSERVATIONS UPON THIS EPIDERMIS.


 I. _Epidermis of the origin of the Mucous Surfaces._

 It is very distinct.—Proofs of its existence.—Its reproduction.—Its
 nature.                                                             366




 II. _Epidermis of the deep Surfaces._

 Uncertainty of its existence.—Experiments.—Membranes that are
 sometimes thrown off.—It appears that it is not the epidermis.      367


 ARTICLE THIRD.

 OF THE NAILS.


 I. _Form, Extent, Relations, &c._

 Of the habit of cutting the nails.—Anterior, middle and posterior
 portions of the nail.—Superior and inferior surfaces.—Of the texture
 which supports the nail.                                            369


 II. _Organization, Properties, &c._

 Of the laminæ which form the nails.—Of their arrangement.—Their
 analogy with the epidermis.—Obscurity of the vital
 properties.—Facility with which the nails, epidermis, &c. are
 coloured.                                                           373

 _Development._—State of the nails in the fœtus, the adult, and the old
 person.                                                             376


 PILOUS SYSTEM.


 GENERAL OBSERVATIONS.


 ARTICLE FIRST.

 EXAMINATION OF THE PILOUS SYSTEM IN THE DIFFERENT REGIONS.


 I. _Pilous System of the Head._

 General observations.                                               379

 _Of the Hair._—Its length, situation, limits, influence on
 physiognomy, variety according to sex, uses, thickness, fundamental
 colours, shades, and influence on temperament.                      381

 _Eyebrows._—Their general arrangement.—Their motions.               386

 _Eyelashes._—Their form, arrangement, &c.                           387

 _Beard._—It is the attribute of the male.—Its relations with
 strength.—Of our habits in relation to the beard.                   388


 II. _Of the Pilous System of the Trunk._

 Its varieties according to the regions.                             390


 III. _Pilous System of the Extremities._

 Its varieties.—It is wanting on the palms of the hands and the soles
 of the feet.                                                      _ib._


 ARTICLE SECOND.

 ORGANIZATION OF THE PILOUS SYSTEM.


 I. _Origin of the Hairs._

 Of the membranous canal which encloses this origin.—Relation of the
 hair with this canal.—Organization of this.—Swelling of the hair and
 its origin.—Its course to the exterior.                             391


 II. _External Covering of the Hairs._

 Analogy of this covering with the epidermis.—Its differences.—Action
 of the different agents upon this covering.—Its external
 arrangement.                                                        394


 III. _Internal Substance of the Hairs._

 We are ignorant of its nature.—Capillaries of the hairs of the
 head.—Their colouring substance.—The internal substance of the hairs
 of the head is essentially subjected to the influence of the vital
 phenomena.—Proof of this assertion.—This distinguishes it from the
 external covering.  396


 ARTICLE THIRD.

 PROPERTIES OF THE PILOUS SYSTEM.

 It undergoes but little horny hardening.—Of curling.—The properties of
 texture slightly marked.—The animal ones are nothing.—The organic are
 a little more evident.                                              401


 ARTICLE FOURTH.

 DEVELOPMENT OF THE PILOUS SYSTEM.


 I. _State of this System in the First Age._

 Of the down of the fœtus.—The growth of the hairs is then the reverse
 of that of the other parts.—Their growth after birth.—Their colours
 are a little deeper in infancy.                                     403


 II. _State of the Pilous System in the following Ages._

 Revolution at puberty.—Of the hairs which then appear.—There are but
 few changes in the following ages.                                  404


 III. _State of the Pilous System in Old Age._

 Of the hairs which die first.—Of the whiteness which they
 then assume.—They grow in this state.—Why.—Do they grow after
 death.—General differences of animate and inanimate bodies in their
 decay.                                                              405


 IV. _Preternatural Development._

 Development upon the mucous surfaces, upon the skin and in cysts.   408

END OF THE THIRD AND LAST VOLUME.

       *       *       *       *       *

Transcriber's Notes

Obvious typographical errors have been silently corrected. Variations
in spelling hyphenation and punctuation remain unchanged, but the use
of ligatures has been standardised.

Italics are represented thus _italic_.








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