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Title: A Lecture on the Preservation of Health

Author: Thomas Garnett

Release date: May 11, 2006 [eBook #18376]

Language: English

Credits: Produced by R. L. Garnett


*** START OF THE PROJECT GUTENBERG EBOOK A LECTURE ON THE PRESERVATION OF HEALTH ***




Produced by R. L. Garnett




A LECTURE
ON THE
PRESERVATION
OF
_HEALTH_.

BY T. GARNETT, M.D.
Professor of Natural Philosophy and Chemistry in the
Royal Institution of Great Britain &c.

SECOND EDITION.

[Figure]

     Such the reward of rude and sober life;
     Of labour such. By _health_ the peasant's toil
     Is well repaid; if _exercise_ were pain
     Indeed, and _temperance_ pain.          _Armstrong_.


_LONDON_:
PRINTED FOR T. CADELL, JUNIOR, AND
W. DAVIES, STRAND. 1800.
(R. NOBLE, Printer, Old Bailey.)

_To ERASMUS DARWIN, M.D._

_Dear Sir,_

_THE first edition of this pamphlet having been introduced to the
world under the sanction of your name, I take the liberty of
prefixing it to the second; and am happy in having another public
opportunity of expressing my thanks for the high gratification and
instruction which I have received from the perusal of your medical
and philosophical works._

_I am,_
_Dear Sir,_
_With much esteem,_
_Your very obedient servant,_

_THO. GARNETT._

_Royal Institution,_
_April 8th, 1800._

_PREFACE._

_Most medical gentlemen will, it is supposed, agree that the greater
part of the numerous train of diseases to which their patients are
subject, have been brought on by improper conduct and imprudence.
That this conduct often proceeds from ignorance of its bad effects,
may be presumed; for though it cannot be denied that some persons
are perfectly regardless with respect to their health, yet the great
mass of mankind are too sensible of the enjoyment and loss of this
greatest of blessings, to run headlong into danger with their eyes
open._

_It was with the hope of making the laws of life more generally
known, and better understood, and from thence deducing such rules
for the preservation of health, as would be evident to every
capacity, that the author was induced to deliver this lecture. It
has been honoured with the attention of numerous audiences, in some
of the most populous towns in England, where it has generally been
read for the benefit of charitable institutions._

_The author flatters himself, that besides the benefit produced by
his humble endeavours to serve these institutions, those endeavours
have not totally failed in the grand object of preserving health;
and with the hope that the influence of the precepts here given, may
be farther extended, he has concurred in the ideas of those who have
advised the publication of this lecture._

_It is to be feared, that notwithstanding all which can be done,
disease will continue to be a heavy tax, which civilized society
must pay for its comforts; and the valetudinarian will often be
tempted to envy the savage the strength and soundness of his
constitution. Much however may be done towards the prevention of a
number of diseases. If this lecture should contribute to the
attainment of so desirable an end, it will afford the highest
gratification to the author._

_The first part of the lecture is the substance of an essay which was
read by the author before the Royal Medical Society of Edinburgh,
intended as a defence of the general principles of the system of Dr.
Brown, whose pupil he then was. It was, according to custom,
transcribed into the books of the society, and the public have now
an opportunity of judging how far Dr. Girtanner, in his first
essay published in the Journal de Physique, about two years after,
in which he gives the theory as his own, without the least
acknowledgment to the much injured and unfortunate author of the_
Elementa Medicinae, _has borrowed from this essay._

_In public lectures, novelty is not to be expected, the principal
object of the lecturer being to place in a proper point of view,
what has been before discovered. The author has therefore freely
availed himself of the labours of others, particularly of the
popular publications of Dr. Beddoes, which he takes this opportunity
of acknowledging._

_This lecture is published almost_ verbatim _as it was delivered. On
this account the experiments mentioned are not minutely described,
the reader being supposed to see them performed._

* * * * *

A LECTURE,
&c.

THE greatest blessing we enjoy is health, without it, wealth,
honors, and every other consideration, would be insipid, and even
irksome; the preservation of this state therefore, naturally
concerns us all. In this lecture, I shall not attempt to teach you
to become your own physicians, for when the barriers of health are
once broken down, and disease has established itself, it requires
the deepest attention, and an accurate acquaintance with the
extensive science of medicine, to combat it; to attain this
knowledge demands the labour of years. But, a majority of the
diseases to which we are subject, are the effects of our own
ignorance or imprudence, and it is often very easy to prevent them;
mere precepts however, have seldom much effect, unless the reasoning
upon them be rendered evident; on this account, I shall first
endeavour, in as plain and easy a manner as possible, to explain to
you the laws by which life is governed; and when we see in what
health consists, we shall be better enabled to take such methods as
may preserve it. Health is the easy and pleasant exercise of all the
functions of the body and mind; and disease consists in the uneasy
and disproportioned exercise of all, or some of the functions.

When dead matter acts upon dead matter, the only effects we perceive
are mechanical, or chemical; for though there may appear to be other
kinds of attraction, or repulsion, such as electric and magnetic,
yet these come under the head of mechanical attraction, as producing
motion; we may therefore lay it down as a law, that when dead, or
inanimate bodies act upon each other, no other than mechanical, or
chemical effects are produced; that is, either motion, or the
decomposition, and new combination of their parts. If one ball
strike another, it communicates to it a certain quantity of motion,
this is called mechanical action; and if a quantity of salt, or
sugar, be put into water, the particles of the salt or sugar will
separate from each other, and join themselves to the particles of
the water; the salt and water in these instances, are said to act on
each other chemically; and in all cases whatever, in which
inanimate, or dead bodies act on each other, the effects produced
are, motion, or chemical attraction.

But, when dead matter acts on those bodies which we call living, the
effects are much different; let us take for example a very simple
instance.--Snakes, at least some species of them, pass the winter in
a torpid state, which has all the appearance of death; now heat, if
applied to dead matter, will only produce motion, or chemical
combination; but if it be applied to the snake, let us see what will
be the consequence; the reptile first begins to move, and opens its
eyes and mouth; when the heat has been applied for some time, it
crawls about in search of food, and performs all the functions of
life. Here then, dead matter, when applied to a living body,
produces living functions; for if the heat had not been applied, the
snake would have continued senseless, and apparently lifeless. In
more perfect animals, the effects produced by the action of dead
matter on them, are more numerous, and are different in different
living systems, but are in general the following--sense and motion
in almost all animals, and in many the power of thinking, and other
affections of the mind. The powers, or dead matters, which are
applied, and which produce these functions, are chiefly, heat, food,
and air. The proof that these powers do produce the living
functions, is in my opinion a very convincing one, namely, that when
their actions are suspended, the living functions cease; take away,
for instance, heat, air, and food from animals, and they soon become
dead matter, and it is not necessary that an animal should be
deprived of all these to put a stop to the living functions; if any
one of them be taken away, the body sooner or later becomes dead
matter: it is found by experience, that if a man be deprived of air,
he dies in about three or four minutes; for instance, if he be
immersed under water; if he be deprived of heat, or in other words,
exposed to a very severe degree of cold, he likewise soon dies; or
if he be deprived of food, his death is equally certain, though more
slow. It is sufficiently evident then, that the living functions are
owing to the action of these external powers upon the body. What I
have here said, is not confined to animals, but the living functions
of vegetables are likewise caused by the action of dead matter upon
them. The dead matters, which by their action produce these
functions, are principally heat, moisture, light, and air. It
clearly follows therefore, from what I have said, that living bodies
must have some property different from dead matter, which renders
them capable of being acted upon by these external powers, so as to
produce the living functions; for if they had not, the only effects
which these powers could produce, would be mechanical, or chemical.
Though we know not exactly in what this property consists, or in what
manner it is acted on, yet we see, that when bodies are possessed of
it, they become capable of being acted upon by external powers, and
thus the living functions are produced; we shall therefore call this
property _excitability_, and in using this term it is necessary to
mention, that I mean only to express a fact, without the least
intention of pointing out the nature of that property which
distinguishes living from dead matter, and in this we have the
example of the great Newton, who called the property which causes
bodies in certain situations to approach each other, _gravitation_,
without in the least hinting at its nature; yet, though he knew not
what gravitation was, he investigated the laws by which bodies were
acted on by it, in the same manner, though we are ignorant of
excitability, or the nature of that property which distinguishes
living from dead matter, we can investigate the laws by which dead
matter acts on living bodies through this medium. We know not what
magnetic attraction is, and yet we can investigate its laws; the
same holds good with regard to electricity; if we ever should attain
a knowledge of the nature of this property, it would make no
alteration in the laws which we had before discovered.

I shall now proceed to the investigation of the laws by which the
excitability is acted on; but I must first define some terms which
it will be necessary to use, to avoid circumlocution, and at the
same time to give us more distinct ideas on the subject.

When the excitability is in such a state as to be very susceptible of
the action of external powers, I shall call it _abundant_, or
_accumulated_; but when it is found not very capable of receiving
their action, I shall say, it is _deficient_, or _exhausted_. I
would not wish however, to have it thought, that by these terms I
mean in the least to hint at the _nature_ of excitability, nor that
it is _really_ one while increased, and at another diminished in
quantity, for the abstract question is in no shape considered; we
know not whether the excitability, or the vital principle, depends
on a particular arrangement of matter, or from whatever cause it may
originate; by the terms here used, I mean only to say, that the
excitability is easily acted on when I call it abundant, or
accumulated; at other times the living body is with more difficulty
excited, and then I say, the vital principle is deficient, or
exhausted.

The laws by which external powers act on living bodies, will, on a
careful examination, be found to be the following--

First, when the powerful action of the exciting powers ceases for
some time, the excitability accumulates, or becomes more capable of
receiving their action, and is more powerfully affected by them.

If we examine separately the different exciting powers, which act on
the body, we shall find abundant confirmation of this law. Let us
first consider Light; if a person be kept in darkness for some time,
and be then brought into a room in which there is only an ordinary
degree of light, it will be almost too oppressive for him, and appear
excessively bright; and if he have been kept for a considerable time
in a very dark place, the sensation will be very painful. In this
case, while the retina, or optic nerve, was deprived of light, its
excitability accumulated, or became more easily affected by light;
for if a person goes out of one room, into another which has an
equal degree of light, he will feel no effect. You may convince
yourselves of this law by a very simple experiment--shut your eyes,
and cover them for a minute or two with your hand, and endeavour not
to think of the light, or of what you are doing; then open them, and
the day-light will for a short time appear brighter. If you look
attentively at a window, for about two minutes, and then cast your
eyes upon a sheet of white paper, the shape of the window-frames
will be perfectly visible upon the paper; those parts which express
the wood-work, appearing brighter than the other parts. The parts of
the optic nerve on which the image of the frame falls, are covered
by the wood-work from the action of the light; the excitability of
these portions of the nerve will therefore accumulate, and the parts
of the paper which fall upon them, must of course appear brighter.
If a person be brought out of a dark room where he has been
confined, into a field covered with snow, when the sun shines, it
has been known to affect him so much, as to deprive him of sight
altogether.

Let us next consider what happens with respect to heat; if heat be
for some time abstracted, the excitability accumulates; or in other
words, if the body be for some time exposed to cold, it is more
liable to be affected by heat, afterwards applied; of this also you
may be convinced by an easy experiment--put one of your hands into
cold water, and then put both into water which is considerably warm;
the hand which has been in cold water, will feel much warmer than
the other. If you handle some snow with one hand, while you keep the
other in your bosom, that it may be of the same heat as the body,
and then bring both within the same distance of the fire, the heat
will affect the cold hand infinitely more than the warm one. This is
a circumstance of the utmost importance, and ought always to be
carefully attended to. When a person has been exposed to a severe
degree of cold for some time, he ought to be cautious how he comes
near a fire, for his excitability will be so much accumulated, that
the heat will act violently; often producing a great degree of
inflammation, and even sometimes mortification. We may by the way
observe, that this is a very common cause of chilblains, and other
inflammations. When the hands, or any other parts of the body have
been exposed to violent cold, they ought first to be put into cold
water, or even rubbed with the snow, and exposed to warmth in the
gentlest manner possible.

Exactly the same takes place with respect to food, if a person have
for some time been deprived of food, or have taken it in small
quantity, whether it be meat or drink; or if he have taken it of a
less stimulating quality, he will find, that when he returns to his
ordinary mode of living, it will have more effect upon him than
before he lived abstemiously.

Persons who have been shut up in a coal-work from the falling in of
the pit, and have had nothing to eat for two or three days, have
been as much intoxicated by a bason of broth, as a person in common
circumstances with two or three bottles of wine; and we all know
that spirituous, or vinous liquors affect the head more in the
morning, than after dinner.

This circumstance was particularly evident among the poor sailors
who were in the boat with Captain Bligh after the mutiny. The
captain was sent by government to convey some plants of the
bread-fruit tree from Otaheite, to the West-Indies; soon after he
left Otaheite, the crew mutinied, and put the captain and most of
the officers, with some of the men, on board the ship's boat, with a
very short allowance of provisions, and particularly of liquors, for
they had only six quarts of rum, and six bottles of wine, for
nineteen people, who were driven by storms about the south-sea,
exposed to wet and cold all the time, for nearly a month; each man
was allowed only a tea-spoon full of rum a-day, but this tea-spoon
full refreshed the poor men, benumbed as they were with cold, and
faint with hunger, more than twenty times the quantity would have
done those who were warm, and well fed; and had it not been for the
spirit having such power to act upon men, in their condition, they
never could have outlived the hardships they experienced. All these
facts, and many others which might be brought, establish beyond a
doubt the truth of the law I have mentioned, namely, that when the
powerful action of the exciting powers ceases for some time, the
excitability accumulates, or becomes more capable of receiving their
actions.

The second law is, that when the exciting powers have acted with
violence, or for a considerable time, the excitability becomes
exhausted, or less fit to be acted on, and this we shall be able to
prove by a similar induction. Let us take the effects of light upon
the eye; when it has acted violently for some time upon the optic
nerve, it diminishes the excitability of that nerve, and renders it
incapable of being affected by a quantity of light that would at
other times affect it. When you have been walking out in the snow,
if you come into your room, you will scarcely be able to see any
thing for some minutes. Look stedfastly at a candle for a minute or
two, and you will with difficulty discern the letters of a book,
which you were before reading distinctly; and if you happen to cast
your eyes upon the sun, you will not see any thing distinctly for
some time afterwards.

Let us next consider the matter of heat: suppose water to be heated
lukewarm, if you put one hand into it, it will feel warm; if you now
put the other hand into water, heated for instance to 120 degrees or
130 degrees, and keep it there some time, we will say, two minutes;
if then you take it out, and put it into the lukewarm water, that
water will feel cold, though still it will seem warm to the other
hand; for, the hand which had been in the heated water, has had its
excitability exhausted by the application of heat. Before you go
into a warm bath, the temperature of the air may seem warm and
agreeable to you, but after you have remained for some time in a
bath that is rather hot, when you come out, you feel the air
uncommonly cool and chilling.

Let us now examine the effects of substances taken into the stomach;
and as the effects of spirituous, and vinous liquors, are a little
more remarkable than food, we shall make our observations upon them.

A person who is unaccustomed to drink these liquors, will be
intoxicated by a quantity that will produce no effect upon one who
has been for some time accustomed to take them; and when a person
has used himself to these stimulants for some time, the ordinary
powers which in common support life, will not have their proper
effects upon him, because his excitability has been in some measure
exhausted by the stimulants.

The same holds good with respect to tobacco and opium; a person
accustomed to take opium will not be affected by a quantity that
would completely intoxicate one not used to it; because the
excitability has been so far exhausted by the use of that drug, that
it cannot be acted on by a small quantity.

These facts, with innumerable others, which will easily suggest
themselves to you, prove the truth of our second proposition,
namely, that when the exciting powers have acted violently, or for a
considerable time, the excitability is exhausted, or less fit to be
acted on.

This exhaustion of the excitability, may, however, be either finite,
or temporary; we see animals, while the exciting powers continue to
act, at first appear in their greatest vigour, then gradually decay,
and at last come into that state, in which, from the long continued
action of the exciting powers, the excitability is entirely
exhausted, and death takes place.

We likewise see plants in the spring, while the exciting powers have
acted on them, moderately, and for a short time, arrayed in their
verdant robes, and adorned with flowers of "many mingling hues;"
but, as the exciting powers which support the life of the plant,
continue to be applied, and some of them, for instance heat, as the
summer advances become increased, they first lose their verdure,
then grow brown, and at the end of summer cease to live; because
their excitability is exhausted by the long continued action of the
exciting powers; and this does not happen merely in consequence of
the heat of summer decreasing, for they grow brown and die, even in
a greater degree of heat than that which in spring made them grow
luxuriantly.

These are examples of the finite, or irreparable exhaustion of the
excitability, but we find also, that it may be exhausted for a time,
and accumulated again. Though the eye has been so dazzled by the
splendour of light, that it cannot see an object moderately
illuminated, yet, if it be shut for some time, the excitability of
the optic nerve accumulates again, and we are again capable of
seeing with an ordinary light.

We find, that we are not always equally capable of performing the
functions of life. When we have been engaged in any exertion, either
mental or corporeal, for some hours only, we find ourselves
fatigued, and unfit to pursue our labours much longer; if in this
state, several of the exciting powers, particularly light and noise,
be withdrawn; and if we are laid in a posture which does not require
much muscular exertion, we soon fall into that state which nature
intended for the accumulation of the excitability, and which we call
Sleep. In this state, many of the exciting powers cannot act upon us,
unless applied with some violence, for we are insensible to their
moderate action. A moderate light, or a moderate noise, does not
affect us, and the power of thinking, which exhausts the
excitability very much, is in a great measure suspended. When the
action of these powers has been suspended for six or eight hours,
the excitability is again capable of being acted on, and we rise
fresh, and vigorous, and fit to engage in our occupations.

Sleep then, is the method which nature has provided to repair the
exhausted constitution, and restore the vital energy; without its
refreshing aid, our worn-out habits would scarcely be able to drag
on a few days, or at most a few weeks, before the vital spring was
quite run down; how properly therefore has the great poet of nature
called sleep the chief nourisher in life's feast.--

     'Sleep, that knits up the ravell'd sleeve of care,
     'the death of each day's life, sore labour's bath,
     'balm of hurt minds, great Nature's second course,
     'chief nourisher in life's feast.'

From the internal sensations often excited, it is natural to
conclude that the nerves of sense are not torpid during sleep; but
that they are only precluded from the perception of external
objects, by the external organs being rendered unfit to transmit to
them the impulses of bodies, during the suspension of the power of
volition; thus, the eye-lids are closed in sleep, to prevent the
impulse of the light from acting on the optic nerve; and it is very
probable that the drum of the ear is not stretched; it is likewise
probable that something similar happens to the external apparatus of
all our organs of sense, which may make them unfit for their office
of perception during sleep.

The more violently the exciting powers have acted, the sooner is
sleep brought on; because the excitability is sooner exhausted, and
therefore, sooner requires the means of renewing it; and on the
contrary, the more weakly the exciting powers have acted, the less
is a person inclined to sleep. Instances of the first are, excess of
exercise, strong liquors, or study, and of the latter, an under
proportion of these.

A person who has been daily accustomed to much exercise, whether
mental or corporeal, if he omit it, will find little or no
inclination to sleep; he may however be made to sleep by taking a
little diffusible stimulus; for instance, a little warm punch, or
opium: these act entirely by exhausting the excitability to that
degree which is compatible with sleep; and when their stimulant
effect is over, the person soon falls into that state.

But though the excitability may have been sufficiently exhausted,
and the action of the external powers considerably moderated, yet
there are some things within ourselves, which stimulate violently,
and prevent sleep; such as pain, thirst, and strong passions and
emotions of the mind. These all tend to drive away sleep, but it may
be induced, by withdrawing the mind from these impressions;
particularly from uneasy emotions, and employing it on something
which makes a less impression; sleep, in such cases, is frequently
brought on by listening to the humming of bees, [1] or the murmuring
of a rivulet; by employing the mind on subjects which do not require
much exertion, nor produce too much commotion; such as counting to a
thousand, or counting drops of water which fall slowly.

It sometimes happens, as has been well observed by Dr. Franklin,
that an uneasy heat of the skin, from a want of perspiration,
occasioned by the heat of the bed-cloaths, will prevent sleep; in
this case, he recommends a method, which I believe will often
succeed--namely, to get up and walk about the room till you are
considerably cooled; when you get into bed again, the heat of the
skin will be diminished, and perspiration become more free, and you
will probably sleep in a very few minutes. [2]

By induction we have discovered two of the principal laws by which
living bodies are governed; the first is, that when the ordinary
powers which support life have been suspended, or their action
lessened for a time, the excitability, or vital principle
accumulates, or becomes more fit to receive their actions; and
secondly, when these powers have been acted upon violently, or for a
considerable time, the excitability is exhausted, or becomes less
fit to receive their actions. There are therefore three states in
which living bodies exist.--

First, a state of accumulated excitability.

Second, a state of exhausted excitability.

Third, when it is in such a state as to produce the strongest and
most healthy actions, when acted upon by the external powers.

From what I have said, it must appear, that life is a forced state,
depending on the action of external powers upon the excitability;
and that, by their continued action, if they are properly regulated,
the excitability will be gradually and insensibly exhausted; and
life will be resigned into the hands of him who gave it, without a
struggle, and without a groan.

We see then, that nature operates in supporting the living part of
the creation, by laws as simple and beautiful as those by which the
inanimate world is governed. In the latter we see the order and
harmony which is observed by the planets, and their satellites, in
their revolution round the great source of heat and light.

          '-----All combin'd
     'and ruled unerring, by that single power
     'which draws the stone projected, to the ground.'

In the animated part of the creation, we observe those beautiful
phenomena which are exhibited by an almost infinite variety of
individuals, all depending upon one simple law, the action of the
exciting powers on the excitability.

I cannot express my admiration of the wisdom of the creator better
than in the words of Thomson.

     'O unprofuse magnificence divine!
     'O wisdom truly perfect! thus to call
     'from a few causes, such a scheme of things;
     'effects so various, beautiful, and great.'

Life then, or those functions which we call living, are the effects
of certain exciting powers, acting on the excitability, or property
distinguishing living from dead matter. When those effects, namely,
the functions, flow easily, pleasantly, and completely, from the
action of the exciting powers, they indicate that state which we
call Health.

I have detained you a long time on this subject, but it is of
importance to make you acquainted with these laws; for it is from a
knowledge of them, that the rules for preserving health must be
deduced; and having rendered them, as I hope, intelligible to you, I
shall proceed to point out such necessary cautions for your conduct,
as are easily deduced from them; and which experience confirms; and
I shall follow an arrangement in the consideration of the subject,
which naturally presents itself to us. The chief exciting powers
which act upon us are, air and food; these I shall respectively
consider, and afterwards make a few remarks on exercise.

The air is the main-spring in the animal machine; the source of heat
and activity, without which our blood would soon become a black and
stagnant mass, and life would soon stop.

It is now known, that only a part of atmospheric air, is necessary
for respiration: the atmosphere near the surface of the earth,
consists of two kinds of air; one, which is highly proper for
respiration, and combustion, and in which, an animal immersed, will
live much longer than in the same quantity of common air; and one,
which is perfectly improper for supporting respiration, or
combustion, for an instant.

The first of these airs, has been called vital air, from its
property of supporting life, and constitutes about one fourth of the
atmosphere. [3] The other, from its property of destroying life, is
called azote, and forms of course the remaining three fourths of the
atmosphere.

These two airs may be separated from each other by various methods.
If a candle be inclosed in a given quantity of atmospheric air, it
will burn only for a certain time, and then be extinguished; and
from the rising of the water in the vessel in which it is inclosed,
it is evident that a quantity of air has been absorbed. What has
been absorbed is the vital air, and what remains, the azote, which
is incapable of supporting flame. If an animal be immersed in a
given quantity of common air, it will live only a certain time; at
the end of this time, the air will be found diminished, about one
fourth being extracted from it, and the remainder will neither
support flame nor animal life; this experiment might easily be made,
but it seems a piece of unnecessary cruelty.

By similar experiments to those I have mentioned, we get the azote
pure; here is some, in which a candle has burnt out, and in which
nothing but azote, or the impure part of the atmosphere is left. [4] I
shall plunge a lighted match into it, and you see it is instantly
extinguished.

Some metals, and particularly manganese, when exposed to the
atmosphere, attract the vital air from it, without touching the
azote; and it may be procured from these metals by the application
of heat, in very great purity. Here is a bottle of that kind of air,
which I have expelled by heat from manganese; I shall plunge a taper
into it, and you will perceive that it burns with great brilliancy.
An animal shut up in it, would live about four times as long as if
shut up in an equal quantity of atmospheric air.

If I take three parts of azote, and one of vital air, I shall form a
compound which is similar to the atmosphere, and which is the
mixture best suited to support the health of the body; for if there
were a much greater proportion of vital air, it would act too
powerfully upon the system, and bring on inflammatory diseases; it
would likewise by its stimulus exhaust the excitability, and bring
us sooner to death; and in the same manner that a candle burns
brighter in vital air, and would therefore be sooner exhausted, so
would the flame of life be sooner burnt out.

On the contrary, if the atmosphere contained a much less proportion
of vital air, it would not stimulate the body sufficiently; the
excitability would morbidly accumulate, and diseases of debility
would occur.

Combustion, putrefaction, and the breathing of animals, are
processes which are continually diminishing the quantity of vital
air contained in the atmosphere; and if the all-wise author of
nature had not provided for its continual re-production, the
atmosphere would in all probability have long since become too
impure to support life; but this is guarded against in a most
beautiful manner.

Water is not a simple element, as has been supposed, but is composed
of vital air, and a particular kind of air which is called
_inflammable_; the same that is used to fill balloons. It has been
found by experiment, that one hundred pounds of water, are composed
of eighty-five pounds of vital air, and fifteen of inflammable
air. [5]

Water may be decompounded by a variety of means, and its component
parts separated from each other.

Vegetables effect this decomposition; they absorb water, and
decompose it in their glands; and taking the inflammable air for
their nourishment, breathe out the vital air in a state of very
great purity; this may be ascertained by a very easy experiment.

This vital air is received by animals into their lungs, gives them
their heat, and communicates a red colour to their blood; when
animals die for want of vital air, their blood is always found
black.

From what I have said, it is evident, that in large and populous
towns, where combustion and respiration are continually performed on
a large scale, the air must be much less pure than in the country,
where there are few of these causes to contaminate the atmosphere,
and where vegetables are continually tending to render it more pure;
and if it was not for the winds which agitate this element, and
constantly occasion its change of place, the air of large towns
would probably soon become unfit for respiration. Winds bring us the
pure air of the country, and take away that from which the vital air
has been in a great measure extracted; but still, from the immense
quantity of fuel which is daily burnt, and the number of people
breathing in large towns, the air very soon becomes impure.

From the greater purity of the air in the country, proceeds the rosy
bloom found in the rural cottage, which we in vain look for in the
stately palace, or the splendid drawing room. Here then are reasons
for preferring the country, which no one will dispute, and whenever
it can be done, such a situation ought always to be chosen in
preference to a large town: this cannot be better enforced than in
the words of Dr. Armstrong.--

     'Ye, who amid the feverish world would wear
     'a body free of pain, of cares a mind;
     'fly the rank city, shun its turbid air;
     'breathe not the chaos of eternal smoke,
     'and volatile corruption, from the dead,
     'the dying, sick'ning, and the living world
     'exhaled, to sully heaven's transparent dome
     'with dim mortality.

         'While yet you breathe, away; the rural wilds
     'invite; the mountains call you, and the vales;
     'the woods, the streams, and each ambrosial breeze
     'that fans the ever undulating sky.'

But there are many whose occupations oblige them to reside in large
towns; they, therefore, should make frequent excursions into the
country, or to such situations as will enable them to enjoy, and to
breathe air of a little more purity. I say _enjoy_, for who that has
been for some time shut up in the town, without breathing the pure
air of the country, does not feel his spirits revived the moment he
emerges from the azote of the town. Let not therefore, if possible,
a single day pass, without enjoying, if but for an hour, the pure
air of the country. Doing this, only for a short time _every_ day,
would be much more effectual than spending whole days, or even weeks
in the country, and then returning into the corrupt atmosphere of
the town; for when you have for a long time breathed an impure air,
the excitability becomes so morbidly accumulated, from the want of
the stimulus of pure air, that the air of the country will have too
great an effect upon you; it will frequently, in the course of a day
or two, bring on an inflammatory fever, attended with stuffing of
the nose, hoarseness, a great degree of heat, and dryness of the
skin, with other symptoms of a violent cold.

Large towns are the graves of the human species; they would perish
in a few generations, if not constantly recruited from the country.
The confined, putrid air, which most of their inhabitants breathe,
their want of natural exercise, but above all their dissipation,
shorten their lives, and ruin their constitutions.

Children particularly, require a pure air; every circumstance points
out the country as the proper place for their education; the purity
of the air, the variety of rustic sports, the plainness of diet, the
simplicity and innocence of manners, all concur to recommend it. It
is a melancholy fact, that above half the children born in London,
die before they are two years old.

To shew how indispensable fresh air is to children, I shall mention
one example which sets the fact in the clearest light. In the
lying-in hospital at Dublin, 2944 infants, out of 7650, died in the
year 1782, within the first fortnight after their birth, which is
nearly every third child; they almost all died in convulsions; many
of them foamed at the mouth, their thumbs were drawn into the palms
of their hands, their jaws were locked, the face was swelled and
looked blue, as though they were choaked. This last circumstance led
the physicians to conclude that the rooms in the hospital were too
close, and hence, that the infants had not a sufficient quantity of
good air to breathe; they therefore set about ventilating them
better, which was done very completely. The consequence has been,
that not one child dies now where three used to die.

Fewer children indeed die convulsed now, than formerly; this is
because the rich learn, either from books, or conversation with
physicians, how necessary fresh air is to life and health; hence
they keep their houses well aired; but the poor, and servants, are
not made to comprehend this matter properly; and therefore from
neglecting to open their windows, and breathing a foul, tainted air,
the greatest part of their time, many disorders are brought on, and
others rendered worse than they naturally would be. [6]

Having considered the purity of the air, let us next take a view of
the changes in temperature which it undergoes, and the effects which
these have upon the constitution.

We find the air sometimes considerably below the freezing point;
nay, even so much as 20 or 30 degrees; it is then intensely cold;
and on the other hand, the thermometer sometimes indicates a great
degree of heat. We then find ourselves much relaxed, and our
constitutions exhausted.

To understand how this happens, let us consider for a moment the
nature of heat, and cold.--Heat is one of those stimuli which act
upon the excitability, and support life: for if it was totally
withdrawn, we should not be able to exist even a few minutes; and
cold is only a diminution of heat. When heat is present, in a proper
degree, or the atmosphere is about that degree of heat which we call
temperate, it just gives such a stimulus, and keeps the excitability
exhausted to such a degree, as to preserve the body in health; but
if it continue for a considerable time to be much warmer than this
temperature, the consequence must be, from the laws already laid
down, an exhaustion of the excitability, and a consequent relaxation
and debility; for, when the excitability has been exhausted by the
violent application of heat, long continued, the common stimulant
powers which support life, cannot produce a sufficient effect upon
it, to give to the body that tone which is compatible with health.
On the contrary, when the heat of the air falls below what we call
temperate, or when cold is applied to the body, from the accustomed
stimulus of heat being diminished, the excitability must accumulate,
or become more liable to be affected by the action of the external
powers.

This, however, very seldom produces bad effects, unless the exciting
powers be improperly or quickly applied; for we can bear a
considerable diminution of heat without any bad consequences; and in
all cases I hope I shall be able to make it appear, that much more
mischief arises from the too great action of heat, than from the
diminution of it. Nature never made any country too cold for its
inhabitants. In cold climates, she has made exercise, and even
fatigue habitual to them, not only from the necessity of their
situation, but from choice; their natural diversions being all of
the athletic or violent kind. But the softness and effeminacy of
modern manners, has both deprived us of our natural defence against
the diseases most incident to our climate, and subjected us to all
the inconveniencies of a warm one.

People are afraid of going out into the cold air; but if they
conduct themselves properly afterwards, they will never be in the
least danger from it. Indeed the action of cold, unless it be
excessive, never produces any bad effects.

Many of you will, no doubt, think me here in an error; but I hope
you will not long entertain that opinion. You will say that you have
had frequent experience to the contrary; that you have often gone
out into the cold air, and have caught dreadful colds. That this is
owing to the action of cold, I will deny; nay, I will assert,
that if a person go out into air which is very cold, _and remain in
it_ for a very long time, he will never perceive any symptoms of
what is called a cold so long as he remains there.

A common cold is attended with a running of the nose, hoarseness,
and cough, with a considerable degree of feverish heat, an dryness
of the skin.--Now it is universally agreed, that this disorder is an
inflammation, or is of an inflammatory nature; it is an inflammation
of the smooth, moist skin which lines the nostrils, and goes down
the wind-pipe into the lungs; but as cold is only a diminution of
heat, or a diminution of a stimulus acting upon the body, it is
impossible that such a diminution can cause a greater action or
excitement; we might as well expect to fill a vessel by taking water
out of it. But let us see how a cold, as it is commonly called, is
usually produced. When a person in cold weather goes out into the
air, every time he draws in his breath, the cold air passes through
his nostrils and windpipe into the lungs, and in thus diminishing
the heat of the parts, allows their excitability to accumulate, and
renders them more liable to be affected by the succeeding heat. So
long as that person continues in the cold air, he feels no bad
effects; but if he come into a warm room, he first perceives a glow
within his nostrils and breast, as well as all over the surface of
the body. Soon afterwards, a disagreeable dryness and huskiness will
be felt in the nostrils and breast. By and by a short, dry, tickling
cough comes on. He feels a shivering, which makes him draw nearer to
the fire, but all to no purpose; the more he tries to heat himself,
the more chill he becomes. All the mischief is here caused by the
violent action of the heat on the accumulated excitability. For want
of a knowledge of this law, these disagreeable, and often dangerous
complaints are brought on; when they might be avoided with the
greatest ease.

When you take a ride into the country on a cold day, you find
yourselves very cold; as soon as you go into a house, you are
invited to come to the fire, and warm yourselves; and what is still
worse, to drink something warm and comfortable, to keep out the
cold, as the saying is. The inevitable consequence of this, is, to
bring on the complaints which I have just described, which might
with more propriety be called, heats than colds. But how easily
might these complaints have been avoided! When you come out of a
very cold atmosphere, you should not at first go into a room that
has a fire in it, or if you cannot avoid that, you should keep for a
considerable time at as great a distance from the fire as possible,
that the accumulated excitability may be gradually exhausted, by the
moderate and gentle action of heat; and then you may bear the heat
of the fire without any danger: but, above all, refrain from taking
warm or strong liquors while you are cold. If a person have his
hands or feet exposed to a very severe cold, the excitability of
those parts will be so much accumulated, that if they should be
brought suddenly near the fire, a violent inflammation, and even a
mortification will take place, which has often happened; or, at any
rate, that inflammation called Chilblains will be produced, from the
violent action of the heat upon the accumulated excitability of
those parts; but, if a person so circumstanced, was to put his hands
or feet into cold water, very little warmer than the atmosphere to
which he had been exposed, or rub them with snow, which is not often
colder than 32 or 30 degrees, the morbid excitability will be
gradually exhausted, and no bad consequences will ensue.

When a part of the body only has been exposed to the action of cold,
and the rest kept heated; if, for instance, a person in a warm room
sits so that a current of air coming through a broken pane, should
fall upon any part of the body, that part will be soon affected with
an inflammation, which is usually called a rheumatic inflammation.
From what has been said, it will be easy to account for this
circumstance. The excitability of the part is accumulated by the
diminution of its heat; but at the same time, the rest of the body
and blood is warm; and this warm blood acting upon a part where the
excitability is accumulated, will cause an inflammation; to which,
the more you apply heat, the worse you make it.--From these
considerations, we may lay it down as a fact, and experience
supports us in so doing, that you may in general go out of warm into
cold air without much danger; but, that you can never return
suddenly from the cold into the warm air with perfect impunity.

Hence, we may lay down the following rule, which, if strictly
observed, would prevent the frequent colds we meet with in winter.
_When the whole body, or any part of it, is chilled, bring it to its
natural feeling and warmth by degrees._

But if, for want of observing this necessary caution, a cold, as it
is called, should have seized a person, let us consider what is
proper to be done.

It will, from the preceding reasoning, appear very improper to make
the room where you sit warmer than usual, to increase the quantity
of bed-clothes, to wrap yourself up in flannel, or particularly to
drink a large quantity of barley-water, gruel, or tea, almost
boiling hot, by way of diluting, as it is called, and forcing a
perspiration; this will infallibly make the disorder worse, in the
same manner as confining inoculated persons in warm rooms would make
their small-pox more violent.

Perhaps there would be scarcely such a thing as a bad cold, if
people, when they found it coming on, were to keep cool, and avoid
wine and strong liquors, and confine themselves for a short time to
a simple diet of vegetable food, drinking only toast and water.
Instances are by no means uncommon, where a heat of the nostrils,
difficulty of breathing, a short, tickling cough, and other
symptoms, threatening a violent cold, have gone off entirely in
consequence of this plan being pursued.

Colds would be much less frequent, were we to take more pains to
accommodate our dress to the season: if we were warmly clothed in
cold weather, our excitability would not be accumulated by the
action of the cold. If a greater proportion of females fall victims
to this disease, is it not because, losing sight, more than men, of
its primary purpose, they regulate their dress solely by fantastic
ideas of elegance? If happily, as is observed by Dr. Beddoes, our
regret should recall the age of chivalry, to break the spell of
fashion would be an atchievement worthy the most gallant of our
future knights. Common sense has always failed in the adventure; and
our ladies, alas! are still compelled, whenever the enchantress
waves her wand, to expose themselves half undressed, to the fogs and
frosts of our climate.

Besides the effects of the air, we ought by no means to be
indifferent with regard to what we take into the stomach as food and
drink; since these have even a greater influence on our health, than
the circumstances I have already mentioned. Among the causes which
excite the body, and support life, I have formerly mentioned food,
or the matters taken into the stomach. It is from these matters that
all the animal solids and fluids are formed; these are stimuli,
which if totally withdrawn, we could not exist many days. These
stimuli are subject to the same laws with all the others which act
upon the body. When they act properly in concert with the other
powers, they produce the healthy state; but if they act in an undue
degree, whether that action be too great or too little, disease will
be the consequence. When they act too feebly, the excitability will
accumulate; and diseases of debility, attended with a very great
degree of irritability, will take place: this has been instanced in
those who have been without food for some time. Persons who have
been shut up in a coal-work by the falling-in of the pit, and have
consequently been without food for some days, have had their
excitability so much accumulated, as to be intoxicated with a bason
of broth.

To this source we may attribute many of the diseases with which the
poor are afflicted; but they are by no means so common as diseases
of an opposite nature, which arise from a too free use of food. I
shall confine myself here to the consideration of what is more
strictly called food, and afterwards consider the effects of strong
liquors.

When we take food in too great quantity, or of too nourishing a
quality, it will either produce inflammatory diseases, such as
pleurisy; or by exhausting the excitability, it will bring on
stomach complaints, gout, and all the symptoms of premature old age.
This follows so evidently from the laws we have investigated, that
it is scarcely necessary to say more on the subject; and I am sure
there are few who have not seen examples of it.

Be therefore temperate in eating, and eat only of such foods as are
the plainest; and let a proper quantity of vegetable food be mixed
with animal. If you value the preservation of health, never satiate
yourselves with eating; but let it be a rule from which you ought
never to depart, always to rise from table with some remains of
appetite: for, when the stomach is loaded with more food than it can
easily digest, a crude and unassimilated chyle is taken into the
blood, pregnant with diseases. Nor is the quantity the only object
of attention; the quality of the food is to be carefully studied;
made dishes, enriched with hot sauces, stimulate infinitely more
than plain food, and therefore exhaust the excitability, bringing on
diseases of indirect debility; such as the worst kind of gout,
apoplexy, and paralytic complaints. "For my part," says an elegant
writer, "when I behold a fashionable table set out in all its
magnificence, I fancy that I see gouts and dropsies, fevers and
lethargies, with other innumerable distempers, lying in ambuscade
among the dishes." Let it be therefore laid down as a rule by those
who wish to preserve their health, and I have nothing to say to
those who are indifferent on that head, to make their chief repast
on one plain dish, and trifle with the rest.

It is by no means uncommon for a medical man to have patients,
chiefly among people of fashion and fortune, who complain of being
hot and restless all night, and having a foul taste in the mouth
every morning: on examination it is found, that in nineteen cases
out of twenty, it has arisen from their having overloaded their
stomachs, and at the same time neglected to take proper exercise;
for it must always be observed, that more may be eaten with safety,
nay, more is even necessary, when a person takes a good deal of
exercise.

When people take little exercise, and overload their stomachs, there
lies within them a fermenting mass of undigested aliment; and it is
not surprizing that this should irritate and heat the body during
the night. This is likewise the foundation of stomach complaints,
flatulencies, and all other symptoms of indigestion; which more
frequently proceed from intemperance in eating and drinking than any
other cause. The benefits arising from temperance are set in a
striking light in the following allegory, which may be found in the
Adventurer.

Esculapius, after his deification or admittance among the gods,
having revisited his native country, and being one day (as curiosity
led him a rambling,) in danger of being benighted, made the best of
his way to a house he saw at some distance, where he was hospitably
received by the master of it. Cremes, for that was the master's
name, though but a young man, was infirm and sickly. Of several
dishes served up to supper, Cremes observed that his guest ate but
of one, and that the most simple; nor could all his intreaties
prevail upon him to do otherwise. He was, notwithstanding, highly
delighted with Esculapius's conversation, in which he observed a
cheerfulness and knowledge superior to any thing he had hitherto met
with.

The next morning, Esculapius took his leave, but not till he had
engaged his good-natured host to pay him a visit at a small villa, a
few miles from thence. Cremes came accordingly, and was most kindly
received; but how great was his amazement when supper was served up,
to see nothing but milk, honey, and a few roots, dressed in the
plainest, but neatest manner, to which hunger, cheerfulness, and
good sense, were the only sauces. Esculapius seemed to eat with
pleasure, while Cremes scarcely tasted of them. On which a repast
was ordered more suitable to the taste of our guest. Immediately
there succeeded a banquet composed of the most artful dishes that
luxury could invent, with great plenty and variety of the richest
and most intoxicating wines. These too were accompanied by damsels
of the most bewitching beauty. Cremes now gave a loose to his
appetites, and every thing he tasted raised ecstasies beyond what he
had ever known. During the repast, the damsels sung and danced to
entertain them; their charms enchanted the enraptured guest, already
flushed with what he had drank; his senses were lost in ecstatic
confusion. Every thing around him seemed Elysium, and he was on the
point of indulging the most boundless freedoms, when on a sudden
their beauty, which was but a vizard, fell off, and discovered forms
the most hideous and forbidding imaginable. Lust, revenge, folly,
murder, meagre poverty, and despair, now appeared in the most odious
shapes, and the place instantly became a most dire scene of misery
and confusion. How often did Cremes wish himself far distant from
such a diabolical company, and now dreaded the fatal consequence
which threatened him. His blood ran chill at his heart, and joy and
rapture were perverted to amazement and horror!--When Esculapius
perceived it had made a sufficient impression on his guest, he thus
addressed him: "Know, Cremes, it is Esculapius who has thus
entertained you, and what you have beheld is a true image of the
deceitfulness and misery inseparable from luxury and intemperance.
Would you be happy, be temperate: temperance is the parent of
health, virtue, wisdom, plenty, and every thing that can make you
happy in this or the world to come. It is indeed the true luxury of
life, for without it life cannot be enjoyed." This said, he
disappeared, and left Cremes (instead of an elegant apartment) in an
open plain, full of ideas quite different from those he had brought
with him.

On his return home, from the most luxurious, he became one of the
most temperate men, by which wise method he soon regained health.
Frugality produced riches, and from an infirm and crazy
constitution, and almost ruined estate, by virtue of this infallible
elixir, he became one of the happiest men breathing, and lived to
a healthy old age, revered as an oracle for his wisdom throughout
all Greece.

If temperance be necessary with regard to food, it is still more so
with respect to strong liquors; these diffusible stimuli, by quickly
exhausting the excitability, soon blast the vigour, and sap the
foundation of the strongest constitution. Their immediate effects
you know are stimulant; they raise the animal spirits, produce a
cheerful state of mind, and if taken in greater quantity, cause
intoxication, or that temporary derangement of the thinking powers
which arises from too great a degree of excitement: but let us see
what happens the next day; the animal spirits are exhausted, and the
person thus situated, finds himself languid and enervated to a great
degree; for it seems a law of the human body, that the spirits are
never artificially raised, without being afterwards proportionably
depressed; and to shew clearly that in this state the excitability
is exhausted, the ordinary powers which in general support life,
will not have their due effect; and a person thus situated finds
most relief the next day, from taking some of the same stimulus
which occasioned the exhaustion; because the common exciting powers
can scarcely act upon his exhausted excitability.

But though the excitability be in this way exhausted, it will in the
course of a day or two be again accumulated, and it may, perhaps, be
suspected that this exhaustion can do no harm to the constitution;
but this is a premature conclusion, and quite contrary to fact and
experience, as well as to reason; for, just in the same manner that
a pendulum, made to vibrate in the arc of a circle, will never
return exactly to the same height, but fall a little short of it
every time; so, though the excitability may be again accumulated, it
never can be brought back to what it was before; and every fresh
debauch will shorten life, probably two or three weeks at least,
besides debilitating the body, and bringing on a variety of
diseases, with premature old age.

Those who drink only a moderate quantity of wine, so as to make them
cheerful, as they call it, but not absolutely to intoxicate, may
imagine that it will do them no harm. The strong and robust may
enjoy the pleasures of the bottle and table with seeming impunity,
and sometimes for many years may not find any bad effects from them;
but depend upon it, if a full diet of animal food be every day
indulged in, with only a moderate portion of wine, its baneful
influence will blast the vigour of the strongest constitution.

While we are eating, water is the best beverage. The custom of
drinking fermented liquors, and particularly wine, during dinner, is
a very pernicious one. The idea that it assists digestion, is false;
those who are acquainted with chemistry know, that food is hardened,
and rendered less digestible by these means, and the stimulus which
wine gives to the stomach is not necessary, excepting to those who
have exhausted the excitability of that organ by the excessive use
of strong liquors. In these. The stomach can scarcely be excited to
any action without the assistance of such a stimulus. If food wants
diluting, water is the best diluent, and will prevent the rising, as
it is called, of strong food, much better than wine or spirits.

Before I finish this subject, I shall say a few words on the
pernicious custom of suffering children to drink wine, or other
fermented liquors. Nothing is more common than to see, even very
young children come to the table after dinner, to drink a glass of
wine. The least quantity produces violent effects on their
accumulated excitability, and by quickly exhausting it, ruins their
constitutions through life, and often renders them habitual
drinkers.

I can scarcely help attributing in some degree the many stomach
complaints we meet with, among young people in the present age, and
which were unknown to our forefathers, to the abominable practice of
suffering children to drink fermented, or spirituous liquors. You
must all have observed how soon children are intoxicated and
inflamed by spirituous liquors; you may judge then, that if these
liquors be only a slow poison to us, they are a very quick one to
them. A glass of wine, on account of the accumulated excitability of
children, will have more effect upon them, than a bottle will have
upon an adult accustomed to drink wine. If therefore, the health of
a child, and its happiness through life be an object, never suffer
it to taste fermented, or spirituous liquors, till it be fifteen or
sixteen years of age, unless a little wine be necessary as a
medicine.

It now only remains for me to take some notice of exercise. Of all
the various methods of preserving health, and of preventing
diseases, which nature has suggested, there is none more efficacious
than exercise; it puts the fluids all in motion, strengthens the
solids, promotes perspiration, and occasions the decomposition of a
larger quantity of atmospheric air in the lungs. Hence, in order to
preserve the health of the body, the author of nature has made
exercise absolutely necessary to the greater part of mankind for
obtaining the means of existence.--Had not exercise been absolutely
necessary for our well-being, says the elegant Addison, nature would
not have made the body so proper for it, by giving such an activity
to the limbs, and such a pliancy to every part, as necessarily
produce those compressions, extensions, contortions, dilatations, and
all other kinds of motions, that are necessary for the preservation
of such a system of tubes and glands.--And that we might not want
inducement to engage us in such exercise of the body as is proper
for its welfare, it is so ordered, that nothing valuable can be
procured without it. Not to mention riches and honors, even food and
raiment are not to be come at without the toil of the hands and
sweat of the brow. Providence furnishes materials, but expects that
we should work them up ourselves. The earth must be laboured before
it gives its increase, and when it is forced into its several
products, how many hands must they pass through before they are fit
for use? Manufactures, trade, and agriculture, naturally employ more
than nineteen parts of the species out of twenty; and as for those
who are not obliged to labour by the condition in which they are
born, they are more miserable than the rest of mankind, unless they
indulge themselves in that voluntary labour which goes by the name
of exercise.

Of all the different kinds of exercise, there is none that conduces
so much to health as riding; it is not attended with the fatigue of
walking, and the free air is more enjoyed in this way than by any
other mode of exercise. Where it cannot be used, walking, or
exercise in a carriage, ought to be substituted.

The best time for taking exercise is before dinner, for the body is
then more vigorous and alert, and the mind more cheerful, and better
disposed to enjoy the pleasure of a ride or walk. Exercise after a
full meal disturbs digestion, and causes painful sensations in the
stomach and bowels, with heart-burn, and acid eructations.

But whatever mode of exercise you use, it ought not at first to be
too violent. Dr. Armstrong has given us an excellent rule--

'Begin with gentle toils, and as your nerves
'grow firm, to hardier, by just steps aspire.
'The prudent, even in every moderate walk,
'at first but saunter, and by slow degrees
'increase their pace.'

THE END.

R. NOBLE. Printer,
   Old Bailey.

NOTES.

[1] Hinc tibi, quae semper vicino ab limine sepes
Hyblaeis apibus florem depasta salicti,
Saepe levi _somnum_ suadebit inire susurro.
     VIRG.

[2] May not the heat, and want of perspiration, depend on an
exhausted irritability of the subcutaneous vessels, which will be
accumulated by the method here recommended?

[3] Oxygen gas, according to the new Nomenclature.

[4] The fixed air, or carbonic acid gas, formed during the
combustion, having been separated by agitation in contact with lime
water.

[5] Strictly speaking, water is composed of the bases of these airs,
the greatest part of the caloric being given out on their union.

[6] Where manufactures are carried on to a great extent, the air is
rendered still worse, and every precaution ought to be used to
preserve the health of the inhabitants. Places where manufactures are
carried on, ought, therefore, to be constructed in such a manner as
to be very lofty, and capable of being easily ventilated.
Night-working is undoubtedly a perversion of the laws of nature,
renders the constitution feeble, and lays a foundation for bad health
and disease: for it not only gives no time for ventilation, and in
consequence the quantity of oxygen becomes more and more exhausted;
but the number of candles used, contributes very much to contaminate
the air. It has been found by experiment that a candle contaminates
more air than a man. By persons who are interested in the welfare of
the succeeding generations, night-work will never be urged, and it
will be right to ventilate the manufactories every night, as well as
during breakfast and dinner.

* * * * *

_Lately published,_
Elegantly printed in Two Volumes Quarto, and illustrated by a Map
and Fifty-two Plates, from Drawings taken on the Spot by W. H.
Watts, who accompanied the Author in the Tour, Price 2l. 12s. 6d. in
Boards,

OBSERVATIONS on a TOUR through the HIGHLANDS and Part of the WESTERN
ISLES of SCOTLAND, particularly STAFFA and ICOLMKILL: To which are
added, a Description of the Falls of the Clyde, of the Country round
Moffat, and an Analysis of its Mineral Waters.

By T. GARNETT, M.D.

Member of the Royal Medical, Physical, and Natural History Societies
of Edinburgh; the Literary and Philosophical Society of Manchester;
the Medical Society of London; the Royal Irish Academy; and
Professor of Natural Philosophy and Chemistry in the Royal
Institution of Great Britain.

Printed for T. Cadell, jun. and W. Davies, Strand.

* * * *

Transcriber's Notes.

The frontispiece contains the following text, and a portrait of the
author:

Engraved by J. Hopwood, from a picture by J. R. Smith.
THOMAS GARNETT, M.D.
Published March 25th 1800, by Cadell & Davies, Strand.

In line 241 of this text, the word transcribed as too appears as o in
the original text, with blank space indicating the omission of the
first two letters of the word. In Lecture IX of Dr. Garnett's
_Zoonomia_, where the same example of the reaction of the eye to light
is given, the word appears as too.








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