Xavier
Bichat
Physiological Researches on Life and Death.
(Translated by F. Gold. Boston: Richardson and Lord, 1827, pp. 9-24.)
General Division
of Life [1].
The definition of life
is usually sought for in abstract considerations; it will be found, if I
mistake not, in the following general expression: Life consists in the sum
of the functions, by which death is resisted. [2]
In living bodies, such
in fact is the mode of existence, that whatever surrounds them, tends to
their destruction. They are influenced incessantly by inorganic bodies; they
exercise themselves, the one upon the other, as constant an action; under
such circumstances they could not long subsist, were they not possessed in
themselves of a permanent principle of reaction. This principle is that of
life; unknown in its nature, it can be only appreciated by its phenomena: an
habitual alternation of action and reaction between exterior bodies, and the
living body, an alternation, of which the proportions vary according to the
age of the latter, is the most general of these phenomena.
There is a
superabundance of life in the child: In the child, the reaction of the
system is superior to the action, which is made upon it from without. In the
adult, action and reaction are on a balance; the turgescence of life is
gone. In the old man, the reaction of the inward principle is lessened, the
action from without remaining unaltered; it is then that life languishes,
and insensibly advances towards its natural term, which ensues when all
proportion ceases.
The measure, then, of
life in general, is the difference which exists between the effort of
exterior power, and that of interior resistance. The excess of the former is
an indication of its weakness; the predominance of the latter an index of
its force.
I. Division of Life
into Animal and Organic Life. [3]
Such is life considered
in the aggregate; examined more in detail it offers us two remarkable
modifications, the one common to the vegetable and the animal; the other
belonging exclusively to the latter. In comparing two individuals from each
of the living kingdoms, the one will be seen existing only within itself,
having with what surrounds it the relations only of nutrition, attached to
the soil, in which its seed has been implanted, born there, growing there,
and perishing there. The other will be observed combining with this interior
life, which in the highest degree it enjoys, an exterior life by which it
acquires a very numerous series of relations with all surrounding bodies, a
life, which couples it to the existence of every other being, by which it is
approximated, or removed from the objects of its desires or its fears, and
seems in appropriating every thing in nature to itself, to consider every
thing with regard to its individual existence only. [4]
Thus it might be said,
that the vegetable is only the sketch, or rather the ground-work of the
animal; that for the formation of the latter, it has only been requisite to
clothe the former with an apparatus of external organs, by which it might be
connected with external objects.
From hence it follows,
that the functions of the animal are of two very different classes. By the
one (which is composed of an habitual succession of assimilation and
excretion) it lives within itself, transforms into its proper substance the
particles of other bodies, and afterwards rejects them when they are become
heterogeneous to its nature. By the other, it lives externally, is the
inhabitant of the world, and not as the vegetable of a spot only; it feels,
it perceives, it reflects on its sensations, it moves according to their
influence, and frequently is enabled to communicate by its voice its
desires, and its fears, its pleasures, and its pains.
The aggregate of the
functions of the first order, I shall name the organic life, because all
organized beings, whether animal or vegetable, enjoy it more or less,
because organic texture is the sole condition necessary to its existence.
The sum of the functions of the second class, because it is exclusively the
property of the animal, I shall denominate the animal life.
The series of the
phenomena of these two lives, relate to the individual. Generation, as a
function, regards the species, and thus has no place among them. Its
connections with the greater number of the other functions are but very
indirect; it commences a long time after them, it is extinct a long time
before them. In the greater number of animals the periods of its activity
are separated by long intervals of time, and during these, it is absolutely
null. Even in man, with whom the remissions of its impulses, are much less
durable, it has not a much more extensive connexion with the rest of the
system. Castration is almost always marked by a general increase of the
nutritive process; the eunuch, enjoying indeed a less degree of vital
energy, but the phenomena of his life being displayed with a greater
exuberance. We shall here, then, lay aside the consideration of the laws
which give us existence, and occupy ourselves alone on those which maintain
us in existence. Of the former we shall speak hereafter.
II. Subdivision of
each of the two lives into two orders of functions.
The animal and the
organic life, are each of them composed of two orders of functions, which
succeed each other, and are concatenated in an inverse direction.
In the animal life, the
first order is established from the exterior of the body, towards the brain;
the second from the brain towards the organs of locomotion and the voice.
The impression of objects successively affects the senses, the nerves and
the brain. The first receive, the second transmit, the third perceives the
impression. The impression, in such way, received, transmitted, and
perceived, constitutes sensation.
The animal, in the first
order of these functions, is almost passive; in the second, he becomes
active.-This second order is the result of the successive actions of the
brain (where volition has been produced in consequence of the previous
sensation) of the nerves, which transmit such volition, and of the
locomotive organs and voice, which are the agents of volition. External
bodies act upon the animal by means of the first order of these functions,
the animal reacts upon them by means of the second.
In general there exists
between the two orders a rigorous proportion; where the one is very marked,
the other is put forth with energy. In the series of living beings, the
animal, which feels the most, moves also the most. The age of lively
perception, is that also of vivacity of motion; in sleep, where the first
order is suspended, the second ceases, or is exercised only with
irregularity. The blind man, who is but half alive to what surrounds him,
moves also with a tardiness which would very soon be lost, were his exterior
communications to be enlarged.
A double movement is
also exercised in the organic life; the one composes, the other decomposes
the animal. Such is the mode of existence in the living body, that what it
was at one time it ceases to be at another. Its organization remains
unaltered, but its elements vary every moment. The molecules of its
nutrition by turns absorbed and rejected, from the animal pass to the plant,
from the plant to inorganic matter, return to the animal, and so proceed in
an endless revolution.
To such revolution the
organic life is well adapted. One order of its functions assimilates to the
animal the substances which are destined to nourish him; another order
deprives him of these substances, when, after having for some time made a
part of it, they are become heterogeneous to his organization.
The first, which is that
of assimilation, results from the functions of digestion, circulation,
respiration, and nutrition. Every particle, which is foreign to the body
before it becomes an element of it, is subject to the influence of these
four functions.
When it has afterwards
concurred for some time to the formation of the organs, the absorbents seize
on it, and throw it out into the circulatory torrent, where it is carried on
anew, and from whence it issues by the pulmonary or cutaneous exhalations,
or by the different secretions by which the fluids are ejected from the body
The second order, then,
of the functions of the organic life, or that of decomposition, is formed of
those of absorption, circulation, exhalation, and secretion.
The sanguiferous system,
in consequence, is a middle system, the center of the organic life, as the
brain is the center of the animal life. In this system the particles, which
are about to be assimilated, are circulated and intermixed with those, which
having been already assimilated, are destined to be rejected; so that the
blood itself is a fluid composed of two parts; the one, the pabulum of all
the parts of the body, and derived from the aliment; the other,
excrementitious, composed of the wrecks and residue of the organs, and the
source of the exterior secretions and exhalations.-Nevertheless these latter
functions serve also, at times, the purpose of transmitting without the
body, the products of digestion, although such products may not have
concurred to the nourishment of the parts. This circumstance may be observed
when urine and sweat are secreted after copious drinking. The skin and the
kidneys being at such times the excreting organs, not of the matter of the
nutritive, but of that of the digestive process; the same also may be said
of the milk of animals, for this is a fluid which certainly has never been
assimilated. [5]
There does not exist
between the two orders of the functions of the organic life the same
relation, which takes place between those of the animal life. The weakness
of the first by no means renders absolutely necessary a decrease of action
in the second. Hence proceed marasmus and leanness, states, in which the
assimilating process ceases in part, the process of excretion remaining
unaltered.
Let us leave, then, to
other sciences, all artificial method, but follow the concatenation of the
phenomena of life, for connecting the ideas which we form of them, and we
shall perceive, that the greater part of the present physiological
divisions, afford us but uncertain bases for the support of any thing like a
solid edifice of science.
These divisions I shall
not recapitulate; the best method of demonstrating their inutility will be,
if I mistake not, to prove the solidity of the division, which I have
adopted. We shall now examine the great differences, which separate the
animal existing without, from the animal existing within, and wearing itself
away in a continual vicissitude of assimilation and excretion.
General Differences
of the Two Lives with Regard to the Outward Form of Their Respective Organs.
The organs of the animal
life are symmetrical, those of the organic life irregular in their
conformation; in this circumstance consists the most essential of their
differences. Such character, however, to some animals, and among the fish,
to the sole and turbot especially, is not applicable; but in man it is
exactly traced, as well as in all the genera which are nearest to him in
perfection. In them alone am I about to examine it.
I. Symmetry of the
external forms of the animal life. [6]
Two globes in every
respect the same, receive the impressions of light. Sounds and odors, have
also their double analogous organ. A single membrane is affected to savors,
but the median line is manifest upon it, and the two segments, which are
indicated by it, are exactly similar. This line indeed is not every where to
be seen in the skin, but it is every where implied. Nature, as it were, has
forgotten to describe it, but from space to space she has laid down a number
of points, which mark its passage. The cleft at the extremity of the nose,
of the chin, and the middle of the lips, the umbilicus, the seam of the
perineum, the projection of the spinous apophyses of the back, and the
hollow at the posterior part of the neck are the principal points at which
it is shown.
The Nerves, which
transmit the impressions received by the senses, are evidently assembled in
symmetrical pairs.
The brain, the organ (on
which the impressions of objects are received) is remarkable also for the
regularity of its form. Its double parts are exactly alike, and even those
which are single, are all of them symmetrically divided by the median line.
The Nerves again, which
transmit to the agents of loco-motion and of the voice, the volitions of the
brain, the locomotive organs also, which are formed in a great degree of the
muscular system, of the bony system, and its dependencies, these together
with the larynx and its accessories, composing the double agents of
volition, have all of them a regularity, a symmetry, which are invariable.
Such even is the truth
of the character which I am now describing, that the muscles and the nerves
immediately cease to be regular, as soon as they cease to appertain to the
animal life. The heart, and the muscular fibers of the intestines are proofs
of this assertion in the muscles; in the nerves, the great sympathetic, is
an evidence of its truth.
We may conclude then
from simple inspection, that Symmetry is the essential character of the
organs of the animal life of man.
II. Irregularity of
the exterior forms of the organic life.
If at present we pass to
the viscera of the organic life, we shall perceive a character directly the
contrary of the former. The stomach, the intestines, the spleen, the liver,
etc. are all of them irregularly disposed.
In the system of the
circulation, the heart and the large vessels, such as the upper divisions of
the aorta, the vena azygos, the vena portae, and the arteria innominata have
no one trace of symmetry. In the vessels of the extremities continual
varieties are also observed, and when they occur, it is particularly
remarkable that their existence on one side in no way affects the other side
of the body.
The apparatus of
respiration appears indeed at first to be exactly regular; nevertheless, the
bronchi are dissimilar in length, diameter, and direction; three lobes
compose one of the lungs, two the other: between these organs also, there is
a manifest difference of volume; the two divisions of the pulmonary artery
resemble each other neither in their course, nor in their diameter; and the
mediastinum is sensibly directed to the left. We shall thus perceive that
symmetry is here apparent only, and that the common law has no exception.
The organs of exhalation
and absorption, the serous membranes, the thoracic duct, the great right
lymphatic vessel, and the secondary absorbents of all the parts have a
distribution universally unequal and irregular.
In the glandular system
also we see the crypts, or mucous follicles disseminated in a disorderly
manner in every part; the pancreas, the liver, the salivary glands
themselves, though at first sight more symmetrical, are not exactly
submitted to the median line; added to this, the kidneys differ from each
other in their situation, in the length and size of their artery and vein,
and in their frequent varieties more especially . [7]
From considerations so
numerous we are led to a result exactly the reverse of the preceding one;
namely, that the especial attribute of the organs of the interior life is
irregularity of exterior form.
III. Consequences
resulting from the difference of exterior form in the organs of the two
lives.
It follows from the
preceding description, that the animal life is as it were double; that its
phenomena performed as they are at the same time on the two sides of the
body, compose a system in each of them independent of the opposite system;
that there is a life to the right, a life to the left; that the one may
exist, the other ceasing to do so, and that they are doubtless intended
reciprocally to supply the place of each other.
The latter circumstance
we may frequently observe in those morbid affections so common, where the
animal sensibility and mobility are enfeebled, or annihilated on one side of
the body, and capable of no affection whatever; where the man on one side is
little more than the vegetable, while on the other he preserves his claim to
the animal character. Undoubtedly those partial palsies, in which the median
line, is the limit where the faculties of sensation and motion finish, and
the origin from whence they begin can never be remarked so invariably in
animals, which, like the oyster, have an irregular exterior.
On the contrary the
organic life is a single system, in which every thing is connected and
concatenated; where the functions on one side cannot be interrupted, and
those on the other subsist. A diseased liver influences the state of the
stomach; if the colon on one side cease to act, that upon the other side
cannot continue in action: the same attack, which arrests the circulation in
the right side of the heart, will annihilate it also in the left side of the
heart. Hence it follows, the internal organs on one side being supposed to
suspend their functions, that those on the other must remain inactive, and
death ensue.
This assertion, however,
is a general one; it is only applicable to the sum of the organic life, and
not to its isolated phenomena. Some of them in fact are double, and their
place may be supplied-the kidneys and lungs are of this description.
I shall not inquire into
the cause of this remarkable difference, which in man, and those animals
which approach him the nearest, distinguishes the organs of the two lives. I
shall only observe, that it enters essentially into the nature of their
phenomena, and that the perfection of the animal functions is so connected
with the general symmetry observed in their respective organs, that every
thing which troubles such symmetry, will more or less impair the functions.
It is from thence, no
doubt, that proceeds this other difference of the two lives, namely, that
nature very rarely varies the usual conformation of the organs of the animal
life. Grimaud has made this observation, but has not shown the principle on
which it depends.
It is a fact, which
cannot have escaped any one the least accustomed to dissection, that the
spleen, the liver, the stomach, the kidneys, the salivary glands, and others
of the internal life, are frequently various in form, size, position, and
direction. Such in the vascular system are these varieties, that scarcely
will any two subjects be found exactly alike under the scalpel of the
anatomist: the organs of absorption, the lymphatic glands in particular, are
rarely the same either in number or volume, neither do the mucous glands in
any way affect a fixed and analogous situation.
And not only is each
particular system subject to frequent aberrations, but the whole of the
organs of the internal life are sometimes found in the inverse of the
natural order. Of this I have lately seen an instance.
Let us now consider the
organs of the animal life, the senses, the brain, the voluntary muscles, and
the larynx: here every thing is exact, precise, and rigorously determined.
In these there is scarcely ever seen a variety of conformation; if there do
exist any, the functions are troubled, disturbed, or destroyed: they remain
unaltered in the organic life, whatever may be the disposition of the parts.
The difference with
respect to action, in the organs of the two lives, depends, undoubtedly,
upon the symmetry of the one, whose functions the least change of
conformation would have disturbed, and on the irregularity of the other,
with which these different changes very well agree.
The functions of every
organ of the animal life are immediately connected with the resemblance of
the organ to its fellow on the opposite side if double, or if single to its
similarity of conformation in its two halves: from hence the influence of
organic changes upon the derangement of the functions may be well conceived.
But this assertion will
become more sensible, when I shall have pointed out the relations which
exist between the symmetry and the irregularity of the organs, and the
harmony and the discordance of their functions.
Notes by François
Magendie
[1] The form adopted by
Bichat, in this work, has been much blamed by some, and extravagantly
praised by others. The blame and the praise appear to me to be equally
misplaced. His object was to exhibit the various phenomena of life; the
order in which this was to be done was a matter of indifference. If Bichat
gave a preference to this form it was because it was conformable to the
nature of his mind; and he accomplished his task in a very happy manner. The
division that he has adopted is not new, it may be found, with slight
modifications in writers of different periods, and even in Aristotle.
Besides, it is not necessary in the sciences to attach a very great
importance to classification. All these contrivances have been invented only
to aid the memory; and the functions of living bodies are not so numerous,
as to render it necessary in studying them to lean upon systematic
divisions.
[2] The word life has been employed by physiologists in two different
senses. With some, it means an imaginary being, the sole principle of all
the functions which living bodies exhibit; with others, it means only the
assemblage of these functions. It is in this last sense that Bichat employs
it. This is what he means to say in the following sentence. Life is the assemblage of the functions
which resist death. He is
wrong only in allowing the idea of death to enter into it; for this idea
necessarily supposes that of life. There is then really a bad circle in this
definition; but in putting aside what is defective in the expression, it may
be seen that Bichat considers life as a result, not as a cause.
Before and since the
time of Bichat, a great number of definitions of life has been given, which
are either false or incomplete. It should not be required of a definition,
that it should give all the properties of the thing which it is designed to
make known, this would be a description; but we have a right to expect that
it should assign to this thing certain characters which belong to it alone,
and thus distinguish it from every thing else.
Let us examine by this
principle the definition adopted in a modern work. Life, it is said, is the
assemblage of the phenomena which succeed each other, for a limited time, in
an organized being. This is
no doubt true of life; but, if it can also be applied to another state, it
ceases to be a definition. An animal has just died; its organs from that
moment are subject to the action of chemical affinities only; decomposition
takes place, gases are disengaged, fluids flow out and new solid aggregates
are formed. After a time every molecular motion ceases; there remains only a
certain number of binary, ternary combinations, etc. Here then is an
assemblage of phenomena taking
place for a limited time in an organized body, and yet it is not life.
[3] This distinction of the two lives is bad, inasmuch as it
tends to separate phenomena which have a very intimate connexion, which
relate to a common object, and which are often produced by means in every
respect similar. Why should I rank among the organs of animal life the
muscular apparatus which carries the alimentary mass from the mouth into the
oesophagus, and among those of the other life, that which takes it from the
cardiac orifice to the anus? Is not the action of the first apparatus in
relation with nutrition as well as the action of the last, and does not the
muscular apparatus of the oesophagus act upon a body which is foreign to us,
as well as that of the tongue and the pharynx? Do the motions of mastication
differ in their object from those of which we have just spoken, and as to
the means of execution, does not the muscular action still perform the
principal part?
We might in the same way
bring near each other the motions by means of which we seize our food. The
action itself of the senses, which directs these motions, is, with
nutrition, in a relation more remote, but not less necessary, and we see in
the various classes of animals that their apparatus is modified according to
the different kinds of nourishment. If the distinction of the two lives be
wanting in justice, as to the object of the functions it separates, we shall
soon see that the characters attached to the organs of one and the other do
not establish this division in a more striking manner.
[4] This division between vegetables and animals is far from
being so striking as is here supposed; these two classes of beings, so
different when we examine them in the individuals endowed with a very
complicated organization, approximate each other in a remarkable degree,
when we descend to those species whose structure is most simple; it is even
remarkable that the most constant character which distinguishes one from the
other, is not found in the organs of animal life, but in those of vegetable
or organic life. The senses are one after the other found wanting; for in an
individual in whom we can discover no nervous system, there is no more
reason to suppose the existence of the sense of touch as a sensation, than
to suppose it in the sensitive plant, the dionaea muscipula, and other
similar plants; we see only action and reaction. The motions of the arms of
certain polypi no more suppose volition than the motion of the root which
follows a wet sponge, or that of the branches which turn towards the light;
the only very constant character is the absence or presence of a digestive
cavity. To speak of an animal as a vegetable clothed with an external
apparatus of organs of relation, is a more brilliant than profound view of
the subject. Buisson, who, in his division of the physiological phenomena,
avoids this inaccuracy, has himself fallen into error; he pretends that
respiration belongs exclusively to animals; and that thus the division of
Bichat was not only,unfounded but also incomplete, since this function,
which is neither of vegetation nor of relation, could be ranked under
neither life. Buisson was not well informed; no doubt the respiration of
vegetables does not exhibit the most apparent phenomena of the respiration
of the mammalia, but every thing, which essentially constitutes the
function, is found in the one as well as in the other; absorption of the
atmospheric air, and the formation and exhalation of a new gas; the rest is
only accidental and is not an appendage but in certain classes of animals.
In some reptiles, though we find a particular organ for respiration, this
organ is not indispensable; it may be removed, and the skin becomes the only
respiratory organ; and when finally we come to consider animals with
tracheae, we see that the conformity becomes more and
more evident.
[5] Bichat seems here to adopt the generally received opinion
that it is the chyle which furnishes to the mammary gland the materials of
which the milk is composed. We know not whence this opinion arises, if it be
not from the gross resemblance which the chyle and milk often exhibit. This
resemblance, if it were very great, would be a poor reason for admitting,
without anatomical proof, so singular a fact; but it is very far from being
perfect. The chyle in fact does not exhibit the milky appearance and the
white opaque color, only when the animal from whom it is taken, has fed upon
substances containing fat; in all other cases, it is almost transparent; its
odor and taste, under all circumstances, differ entirely from those of milk;
if these two fluids are left to themselves, the milk remains a long time
without coagulating, but the chyle almost immediately coagulates, and then
separates into three parts. The solid portion soon exhibits cells, and an
appearance of organization; nothing similar is seen in the cogulum of milk;
the serum of the milk remains colorless when exposed to the simple contact
of the air, that of the chyle assumes a rosy tint, often very vivid.
Finally, if we examine the chemical composition of these two fluids, we
shall find in them differences still more striking. (See for further
details, my Elements of
Physiology Vol. 2.)
[6] It is rather to the external forms that symmetry appears
to have been primitively attached, and it is in some measure accidentally
and because the nature of their functions requires in general that they
should be placed on the exterior, that the organs of relation are found
modified in virtue of this law. In the example cited, of fishes without a
bladder, the eyes, to lose nothing of their utility, must be differently
placed, and on the face, which alone is in relation with the light; yet even
in this case, the symmetry of external forms has been displaced rather than
destroyed, and at the first examination it seems complete. When the organs
of relation are found placed on the interior, they frequently exhibit some
irregularity, and to take an example of a known animal, the organ of voice,
in the male duck, is a very remarkable one; in man even, the wind-pipe is
not symmetrical, after it arrives at the first division of the bronchia. On
the contrary, among the organs of the other life, those which are prominent
on the exterior, constantly present the symmetrical character, as the
thyroid gland, the mammary glands, etc.
[7] If we deny symmetry to the kidneys, because they are not
uniformly composed of the same number of lobes in children, we must deny it
also to the brain, the two lobes of which never exhibit the same arrangement
in their circumvolutions; if we deny it to the salivary glands, because one
is larger than the other, we must deny it to the extremities, because the
right is usually more developed than the left. If these examples are not
enough, a host of others might be cited; such as, the atrabiliary capsules,
the bladder, the different organs of generation and lactation, and the very
regular arrangement of the mucous follicles in certain parts situated upon
the median line, etc. As to the anomalies that are observed in the
distribution of the bloodvessels, they are also observed very frequently,
though in a less evident manner, in the distribution of the nervous
branches.