of the disease, where it had appeared to be improper in its first stage.
The cases which required bleeding were far from being general. I saw two
instances of syncope of an alarming nature, after the loss of ten ounces
of blood; and I heard of one instance of a boy who died in half an hour
after this evacuation.
I remarked that purges of all kinds worked more violently than usual in
this disease.
The convalescence from it was very slow, and a general languor appeared
to pervade the citizens for several weeks after it left the city.
The month of December, 1790, was extremely and uniformly cold. In the
beginning of the month of January, 1791, the weather moderated, and
continued to be pleasant till the 17th, on which day the navigation
of the Delaware, which had been completely obstructed by the ice,
was opened so as to admit of the arrival of several vessels. During
the month of December many people complained of _colds_; but they
were ascribed wholly to the weather. In January four or five persons
in a family were affected by colds at the same time; which created
a suspicion of a return of the influenza. This suspicion was soon
confirmed by accounts of its prevailing in the neighbouring counties of
Chester and Montgomery, in Pennsylvania, and in the distant states of
Virginia and Rhode-Island. It did not affect near so generally as in the
two former times of appearance. There was no difference in the method of
treating it. While the common inflammatory diseases of the winter bore
the lancet as usual, it was remarked that patients who were attacked by
the influenza, did not bear bleeding in a greater proportion, or in a
larger quantity, than in the two former times of its appearance in the
city.
I shall conclude this account of the influenza by the following
observations:
1. It exists independently of the sensible qualities of the air, and in
all kinds of weather. Dr. Patrick Russel has proved the plague to be
equally independent of the influence of the sensible qualities of the
atmosphere, to a certain degree.
2. The influenza passes with the utmost rapidity through a country, and
affects the greatest number of people, in a given time, of any disease
in the world.
3. It appears from the histories of it which are upon record, that
neither climate, nor the different states of society, have produced any
_material_ change in the disease. This will appear from comparing the
account I have given, with the histories of it which have lately been
given by Dr. Grey, Dr. Hamilton, Dr. A. Fothergill, Mr. Chisholm, and
other modern physicians. It appears further, that even time itself has
not been able materially to change the type of this disease. This is
evident, from comparing modern accounts of it with those which have been
handed down to us by ancient physicians.
I have hinted in a former essay at the _diminutives_ of certain
diseases. There is a state of influenza, which is less violent and more
local, than that which has been described. It generally prevails in the
winter season. It seems to originate from a morbid matter, generated
in crowded and heated churches, and other assemblies of the people. I
have seen a cold, or influenza, frequently universal in Philadelphia,
which I have distinctly traced to this source. It would seem as if the
same species of diseases resembled pictures, and that while some of them
partook of the deep and vivid nature of mosaic work, others appeared
like the feeble and transient impressions of water colours.
AN INQUIRY
INTO THE
_CAUSE OF ANIMAL LIFE_.
IN THREE LECTURES,
DELIVERED IN THE UNIVERSITY OF PENNSYLVANIA.
LECTURE I.
GENTLEMEN,
My business in this chair is to teach the institutes of medicine. They
have been divided into physiology, pathology, and therapeutics. The
objects of the first are, the laws of the human body in its healthy
state. The second includes the history of the causes and seats of
diseases. The subjects of the third are the remedies for those diseases.
In entering upon the first part of our course, I am met by a remark
delivered by Dr. Hunter in his introductory lectures to his course of
anatomy. "In our branch (says the doctor) those teachers who study to
captivate young minds with ingenious speculations, will not leave a
reputation behind them that will outlive them half a century. When they
cease from their labours, their labours will be buried along with them.
There never was a man more followed and admired in physiology, than Dr.
Boerhaave. I remember the veneration in which he was held. And now, in
the space of forty years, his physiology is---- it shocks me to think in
what a light it appears[89]." Painful as this premonition may be to the
teachers of physiology, it should not deter them from speculating upon
physiological subjects. Simple anatomy is a mass of dead matter. It is
physiology which infuses life into it. A knowledge of the structure of
the human body occupies only the memory. Physiology introduces it to the
higher and more noble faculties of the mind. The component parts of the
body may be compared to the materials of a house, lying without order
in a yard. It is physiology, like a skilful architect, which connects
them together, so as to form from them an elegant and useful building.
The writers against physiology resemble, in one particular, the writers
against luxury. They forget that the functions they know and describe
belong to the science of physiology; just as the declaimers against
luxury forget that all the conveniences which they enjoy beyond what are
possessed in the most simple stage of society, belong to the luxuries of
life. The anatomist who describes the circulation of the blood, acts
the part of a physiologist, as much as he does, who attempts to explain
the functions of the brain. In this respect Dr. Hunter did honour to
our science; for few men ever explained that subject, and many others
equally physiological, with more perspicuity and eloquence, than that
illustrious anatomist. Upon all new and difficult subjects there must
be pioneers. It has been my lot to be called to this office of hazard
and drudgery; and if in discharging its duties I should meet the fate
of my predecessors, in this branch of medicine, I shall not perish in
vain. My errors, like the bodies of those who fall in forcing a breach,
will serve to compose a bridge for those who shall come after me, in
our present difficult enterprise. This consideration, aided by just
views of the nature and extent of moral obligation, will overbalance the
evils anticipated by Dr. Hunter, from the loss of posthumous fame. Had
a prophetic voice whispered in the ear of Dr. Boerhaave in the evening
of his life, that in the short period of forty years, the memory of
his physiological works would perish from the earth, I am satisfied,
from the knowledge we have of his elevated genius and piety, he would
have treated the prediction with the same indifference that he would
have done, had he been told, that in the same time, his name should be
erased from a pane of glass, in a noisy and vulgar country tavern.
[89] Lect. xi. p. 198.
The subjects of the lectures I am about to deliver, you will find in a
syllabus which I have prepared and published, for the purpose of giving
you a succinct view of the extent and connection of our course. Some of
these subjects will be new in lectures upon the institutes of medicine,
particularly those which relate to morals, metaphysics, and theology.
However thorny these questions may appear, we must approach and handle
them; for they are intimately connected with the history of the
faculties and operations of the human mind; and these form an essential
part of the animal economy. Perhaps it is because physicians have
hitherto been restrained from investigating, and deciding upon these
subjects, by an erroneous belief that they belong exclusively to another
profession, that physiology has so long been an obscure and conjectural
science.
In beholding the human body, the first thing that strikes us, is its
_life_. This, of course, should be the first object of our inquiries.
It is a most important subject; for the end of all the studies of a
physician is to preserve life; and this cannot be perfectly done, until
we know in what it consists.
I include in animal life, as applied to the human body, _motion_,
_sensation_, and _thought_. These three, when united, compose perfect
life. It may exist without thought, or sensation; but neither sensation,
nor thought, can exist without motion. The lowest grade of life,
probably exists in the absence of even motion, as I shall mention
hereafter. I have preferred the term _motion_ to those of oscillation
and vibration, which have been employed by Dr. Hartley in explaining the
laws of animal matter; because I conceived it to be more simple, and
better adapted to common apprehension.
In treating upon this subject, I shall first consider animal life as it
appears in the waking and sleeping states in a healthy adult, and shall
afterwards inquire into the modification of its causes in the f[oe]tal,
infant, youthful, and middle states of life, in certain diseases, in
different states of society, in different climates, and in different
animals.
I shall begin by delivering three general propositions.
I. Every part of the human body (the nails and hair excepted) is endowed
with sensibility, or excitability, or with both of them. By sensibility
is meant the power of having sensation excited by the action of
impressions. Excitability denotes that property in the human body, by
which motion is excited by means of impressions. This property has been
called by several other names, such as irritability, contractility,
mobility, and stimulability.
I shall make use of the term excitability, for the most part, in
preference to any of them. I mean by it, a capacity of imperceptible,
as well as obvious motion. It is of no consequence to our present
inquiries, whether this excitability be a quality of animal matter, or a
substance. The latter opinion has been maintained by Dr. Girtanner, and
has some probability in its favour.
II. The whole human body is so formed and connected, that impressions
made in the healthy state upon one part, excite motion, or sensation,
or both, in every other part of the body. From this view, it appears
to be a unit, or a simple and indivisible quality, or substance. Its
capacity for receiving motion, and sensation, is variously modified by
means of what are called the senses. It is external, and internal. The
impressions which act upon it shall be ennumerated in order.
III. Life is the _effect_ of certain stimuli acting upon the sensibility
and excitability which are extended, in different degrees, over every
external and internal part of the body. These stimuli are as necessary
to its existence, as air is to flame. Animal life is truly (to use the
words of Dr. Brown) "a forced state." I have said the _words_ of Dr.
Brown; for the opinion was delivered by Dr. Cullen in the university of
Edinburgh, in the year 1766, and was detailed by me in this school, many
years before the name of Dr. Brown was known as teacher of medicine.
It is true, Dr. Cullen afterwards deserted it; but it is equally true,
I never did; and the belief of it has been the foundation of many of
the principles and modes of practice in medicine which I have since
adopted. In a lecture which I delivered in the year 1771, I find the
following words, which are taken from a manuscript copy of lectures
given by Dr. Cullen upon the institutes of medicine. "The human body
is not an automaton, or self-moving machine; but is kept alive and in
motion, by the constant action of stimuli upon it." In thus ascribing
the discovery of the cause of life which I shall endeavour to establish,
to Dr. Cullen, let it not be supposed I mean to detract from the genius
and merit of Dr. Brown. To his intrepidity in reviving and propagating
it, as well as for the many other truths contained in his system of
medicine, posterity, I have no doubt, will do him ample justice, after
the errors that are blended with them have been corrected, by their
unsuccessful application to the cure of diseases.
Agreeably to our last proposition, I proceed to remark, that the action
of the brain, the diastole and systole of the heart, the pulsation of
the arteries, the contraction of the muscles, the peristaltic motion of
the bowels, the absorbing power of the lymphatics, secretion, excretion,
hearing, seeing, smelling, taste, and the sense of touch, nay more,
thought itself, are all the effects of stimuli acting upon the organs
of sense and motion. These stimuli have been divided into external and
internal. The external are light, sound, odours, air, heat, exercise,
and the pleasures of the senses. The internal stimuli are food, drinks,
chyle, the blood, a certain tension of the glands, which contain
secreted liquors, and the exercises of the faculties of the mind; each
of which I shall treat in the order in which they have been mentioned.
1. Of external stimuli. The first of these is light. It is remarkable
that the progenitor of the human race was not brought into existence
until all the luminaries of heaven were created. Light acts chiefly
through the medium of the organs of vision. Its influence upon animal
life is feeble, compared with some other stimuli to be mentioned
hereafter; but it has its proportion of force. Sleep has been said
to be a tendency to death; now the absence of light we know invites
to sleep, and the return of it excites the waking state. The late Mr.
Rittenhouse informed me, that for many years he had constantly awoke
with the first dawn of the morning light, both in summer and winter. Its
influence upon the animal spirits strongly demonstrates its connection
with animal life, and hence we find a cheerful and a depressed state of
mind in many people, and more especially in invalids, to be intimately
connected with the presence or absence of the rays of the sun. The
well-known pedestrian traveller, Mr. Stewart, in one of his visits to
this city, informed me, that he had spent a summer in Lapland, in the
latitude of 69°, during the greatest part of which time the sun was
seldom out of sight. He enjoyed, he said, during this period, uncommon
health and spirits, both of which he ascribed to the long duration, and
invigorating influence of light. These facts will surprise us less when
we attend to the effects of light upon vegetables. Some of them lose
their colour by being deprived of it; many of them discover a partiality
to it in the direction of their flowers; and all of them discharge their
pure air only while they are exposed to it[90].
[90] "Organization, sensation, spontaneous motion, and life, exist
only at the surface of the earth, and in places exposed to
_light_. We might affirm the flame of Prometheus's torch was
the expression of a philosophical truth that did not escape
the ancients. Without light, nature was lifeless, inanimate,
and dead. A benevolent God, by producing life, has spread
organization, sensation, and thought over the surface of the
earth."--_Lavoisier._
2. Sound has an extensive influence upon human life. Its numerous
artificial and natural sources need not be mentioned. I shall only take
notice, that the currents of winds, the passage of insects through
the air, and even the growth of vegetables, are all attended with an
emission of sound; and although they become imperceptible from habit,
yet there is reason to believe they all act upon the body, through
the medium of the ears. The existence of these sounds is established
by the reports of persons who have ascended two or three miles from
the earth in a balloon. They tell us that the silence which prevails
in those regions of the air is so new and complete, as to produce an
awful solemnity in their minds. It is not necessary that these sounds
should excite sensation or perception, in order to their exerting a
degree of stimulus upon the body. There are a hundred impressions
daily made upon it, which from habit are not followed by sensation.
The stimulus of aliment upon the stomach, and of blood upon the heart
and arteries, probably cease to be felt, only from the influence of
habit. The exercise of walking, which was originally the result of a
deliberate act of the will, is performed from habit without the least
degree of consciousness. It is unfortunate for this, and many other
parts of physiology, that we forget what passed in our minds the first
two or three years of our lives. Could we recollect the manner in
which we acquired our first ideas, and the progress of our knowledge
with the evolution of our senses and faculties, it would relieve us
from many difficulties and controversies upon this subject. Perhaps
this forgetfulness by children, of the origin and progress of their
knowledge, might be remedied by our attending more closely to the
first effects of impressions, sensation, and perception upon them,
as discovered by their little actions; all of which probably have a
meaning, as determined as any of the actions of men or women.
The influence of sounds of a certain kind in producing excitement, and
thereby increasing life, cannot be denied. Fear produces debility, which
is a tendency to death. Sound obviates this debility, and thus restores
the system to the natural and healthy grade of life. The school-boy and
the clown invigorate their feeble and trembling limbs by whistling or
singing as they pass by a country church-yard, and the soldier feels
his departing life recalled in the onset of a battle by the noise
of the fife, and of the poet's "spirit stirring drum." Intoxication
is frequently attended with a higher degree of life than is natural.
Now sound we know will produce this with a very moderate portion of
fermented liquor; hence we find men are more easily and highly excited
by it at public entertainments where there is music, loud talking,
and hallooing, than in private companies where there is no auxiliary
stimulus added to that of the wine. I wish these effects of sound upon
animal life to be remembered; for I shall mention it hereafter as a
remedy for the weak state of life in many diseases, and shall relate
an instance in which a scream suddenly extorted by grief, proved the
means of resuscitating a person who was supposed to be dead, and who had
exhibited the usual recent marks of the extinction of life.
I shall conclude this head by remarking, that persons who are destitute
of hearing and seeing possess life in a more languid state than other
people; and hence arise the dulness and want of spirits which they
discover in their intercourse with the world.
3. Odours have a sensible effect in promoting animal life. The greater
healthiness of the country, than cities, is derived in part from the
effluvia of odoriferous plants, which float in the atmosphere in the
spring and summer months, acting upon the system, through the medium of
the sense of smelling. The effects of odours upon animal life appear
still more obvious in the sudden revival of it, which they produce in
cases of fainting. Here the smell of a few drops of hartshorn, or even
of a burnt feather, has frequently in a few minutes restored the system,
from a state of weakness bordering upon death, to an equable and regular
degree of excitement.
4. Air acts as a powerful stimulus upon the system, through the medium
of the lungs. The component parts of this fluid, and its decomposition
in the lungs, will be considered in another place[91]. I shall only
remark here, that the circulation of the blood has been ascribed, by
Dr. Goodwin, exclusively to the action of air upon the lungs and heart.
Does the external air act upon any other part of the body besides those
which have been mentioned? It is probable it does, and that we lose
our sensation and consciousness of it by habit. It is certain children
cry, for the most part, as soon as they come into the world. May not
this be the effect of the sudden impression of air upon the tender
surface of their bodies? And may not the red colour of their skins be
occasioned by an irritation excited on them by the stimulus of the air?
It is certain it acts powerfully upon denudated animal fibres; for
who has not observed a sore, and even the skin when deprived of its
cuticle, to be affected, when long exposed to the air, with pain and
inflammation? The stimulus of air, in promoting the natural actions of
the alimentary canal, cannot be doubted. A certain portion of it seems
to be necessarily present in the bowels in a healthy state.
[91] It is probable, the first impulse of life was imparted to the body
of Adam by the decomposition of air in his lungs. I infer this
from the account given by Moses of his creation, in Genesis,
chap. ii. v. 7. "And the Lord God formed man of the dust of the
ground, and breathed into his nostrils the breath of life," in
consequence of which, the verse adds, he became "a living soul."
This explanation of the origin of life in the father of the human
race, appears to accord more with reason, as well as the order
of the words which describe it, than the common opinion of his
having been animated by the infusion of a living soul into his
body.
5. Heat is a uniform and active stimulus in promoting life. It is
derived, in certain seasons and countries, in part from the sun; but its
principal source is from the lungs, in which it appears to be generated
by the decomposition of pure air, and from whence it is conveyed, by
means of the circulation, to every part of the body. The extensive
influence of heat upon animal life, is evident from its decay and
suspension during the winter in certain animals, and from its revival
upon the approach and action of the vernal sun. It is true, life is
diminished much less in man, from the distance and absence of the sun,
than in other animals; but this must be ascribed to his possessing
reason in so high a degree, as to enable him to supply the abstraction
of heat, by the action of other stimuli upon his system.
6. Exercise acts as a stimulus upon the body in various ways. Its first
impression is upon the muscles. These act upon the blood-vessels, and
they upon the nerves and brain. The necessity of exercise to animal life
is indicated, by its being kindly imposed upon man in paradise. The
change which the human body underwent by the fall, rendered the same
salutary stimulus necessary to its life, in the more active form of
labour. But we are not to suppose, that motion is excited in the body by
exercise or labour alone. It is constantly stimulated by the positions
of standing, sitting, and lying upon the sides; all of which act more or
less upon muscular fibres, and by their means, upon every part of the
system.
7. The pleasures we derive from our senses have a powerful and extensive
influence upon human life. The number of these pleasures, and their
proximate cause, will form an agreeable subject for two or three future
lectures.
We proceed next to consider the internal stimuli which produce animal
life. These are