Read Ebook: Physiological Researches on Life and Death by Bichat Xavier Magendie Fran Ois Contributor Gold F Translator Hayward George Translator

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FOOTNOTES:

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.

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.

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.

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 colour, only when the animal from whom it is taken, has fed upon substances containing fat; in all other cases, it is almost transparent; its odour 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 coagulum of milk; the serum of the milk remains colourless 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.

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.

Two globes in every respect the same, receive the impressions of light. Sounds and odours, have also their double analogous organ. A single membrane is affected to savours, 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 shewn.

The Nerves, which transmit the impressions received by the senses, are evidently assembled in symmetrical pairs.

The brain, the organ 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 locomotion 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 fibres 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.

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, &c. 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.

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.

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 enquire 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 shewn 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 rigourously 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.

FOOTNOTES:

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, &c.

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, &c. As to the anomalies that are observed in the distribution of the blood-vessels, they are also observed very frequently, though in a less evident manner, in the distribution of the nervous branches.

GENERAL DIFFERENCE OF THE TWO LIVES WITH REGARD TO THE MODE OF ACTION OF THEIR RESPECTIVE ORGANS.

Harmony is to the functions of the organs, what symmetry is to their conformation; it supposes a perfect equality of force and action, between their similar parts, just as symmetry indicates an exact analogy of external form, and internal structure: indeed it is a necessary consequence of symmetry, for two parts essentially alike in structure, cannot much differ in their manner of action. Hence we should be naturally led to the following conclusion, namely, that harmony is the character of the animal, discordance that of the organic functions. But on these points we must be more particular.

We have already observed, that the animal life arises from the successive actions of the senses, the nerves, the brain, the locomotive organs, and the voice. We shall now consider what harmony of action is, in each of these great divisions.

The precision of our sensations appears to be the more complete in proportion as there exists a resemblance between the two impressions, of which they are each of them the assemblage. We see inaccurately when one of the eyes is better formed, and stronger than the other; when it conveys to the brain a clearer image than its fellow does. It is to avoid this confusion that we shut one eye, while the action of the other is increased by the application of a lens, for at such time there can be no harmony of action in the two organs; accordingly, we make use of one of them only in order to avoid the discordance of the impression.--What a lens applied to one eye only produces artificially, is exemplified in a natural way by squinting.--We squint, says Buffon, because we turn the weaker eye from the object on which the stronger is fixed; for in so doing we avoid the confusion, which would arise from the perception of two dissimilar images.

We know that many other causes may contribute to the production of this effect, but we cannot doubt the reality of the reason assigned. We know also, that in some animals each eye may act without the assistance of the other, and that two different objects may be transmitted at the same time by the two eyes of certain other animals; but this circumstance, when the action of both the organs is united upon a single object, should by no means prevent a similarity in the two impressions. A single sensation is the consequence of the combination; but in what way can such sensation be formed with accuracy, if the same body at the same time be pictured both in strong and weak colours on the one and the other of the retinae?

What we have said of the eye may be equally well applied to the ear. If, of the two sensations which form a sound, the one be received by a strong and well formed organ, the other by a weak one, the impressions will be unequal; the brain also, because it is differently affected by each, will be the seat of an imperfect perception. Such conformation constitutes what is called an incorrect or false ear. For what reason does it happen that one man is unpleasantly affected by a dissonance, while another does not even perceive it? The reason is this, that in the one, the two perceptions of the same sound are identical; in the other, dissimilar. For the same reason a man with a correct ear will combine his dancing with the cadence of the measure given him; another without this similarity of organ will be as constantly at variance in his motions with the orchestra.

Buffon has confined his observations on harmony of action, to the organs of vision and hearing; we shall push our examination of it farther.

In the sense of smelling, as well as in the other senses, we must admit of two impressions; the one primitive, and belonging to the organ, the other consecutive, and affecting the sensorium: now the latter may vary, the former remaining unaltered. Many odours are disagreeable to some, but pleasant to others; and this, not because there is any difference in the affection of the pituitary membrane, but because in different individuals, the mind may attach a very different sentiment to the same impression.--Hence a variety of results does not in this case suppose a difference of principle.

But sometimes the impression which is made upon the pituitary membrane does really differ from that which it ought to be, for producing perfect sensation. Two dogs pursue the same game; the one never loses scent, but makes the same turnings and windings with the animal before him; the other follows his game also, but often stops and hesitates, endeavors to recover the scent, proceeds and stops again. The first of these receives a lively impression of the scented emanation; the organs of the second are only confusedly affected. Now it may be asked whether this confusion does not arise from the unequal action of the two nostrils, from the superior organization of the one, and from the imperfection of the other?--the following observations appear to decide the question.

In the coryza, which affects but one of the nostrils, if the two be suffered to remain open, the sense of smelling is confused; but let the diseased nostril be shut, and the smell shall immediately become distinct. A polypus in one of the nostrils debilitates the action of the pituitary membrane on the affected side, the other remaining in its healthy state: hence, as in the preceding case, ensues a want of harmony in the two organs, and the same confusion in the perception of odours. The greater number of the affections of a single nostril have similar effects, which may be all of them corrected by the same means. And wherefore? because in rendering one of the pituitary membranes inactive, we put a stop to the discordance which is occasioned by the deficiency of action in the other. From the above facts we may conclude, that when the perception is naturally inaccurate, there is a natural dissimilarity in the formation of the organs, and therefore a difference of power in them.

The same reasoning may be applied to the sense of taste. It is often the case that one side of the tongue is affected by palsy or spasm, the median line dividing the insensible half from the other, which continues to preserve its sensibility. But such affection may take place in a variety of degrees, and one side of the tongue retain a power of perceiving savours though in a less perfection than the other side. In such case it is natural to suppose that the taste must be confused; because a clear perception cannot be the consequence of two unequal sensations.

The perfection of the touch as well as that of the other senses, is essentially connected with uniformity of action in the two symmetrical halves of the body, and particularly in the hands. Let us suppose, for instance, a man born blind, to have one hand well organized, the other defective in the power of moving the thumb and fingers, and forming only a stiff and immovable surface; such person would find it a very difficult thing to acquire a just notion of the size and figure of bodies, because the same sensation would not arise from the successive application of each hand to the same substance. Let both of his hands, for example, be supposed to touch a small sphere; the one by the extremities of the fingers will embrace it in all its diameters, and convey to him the idea of roundness; the other, which will be in contact with it only in a few points, will produce a very different sensation. Embarrassed between these two bases of his judgment, he will scarcely be able to decide, nay, it is even possible that he may form a double judgment from the double sensation which is presented him: his ideas would be more correct were he to use only the perfect hand, in the same manner as the person who squints, makes use of the perfect eye only. Our hands then assist each other reciprocally; the one confirms the notions which are given us by the other; hence the necessary uniformity of their conformation.

The hands are not the only instruments of the sense of touch. The axilla, the groin, the concavity of the foot and many other parts, may all of them from their application to bodies, afford us so many bases for our judgments with regard to external form. Now, if one half of the body were differently arranged from the other half, the same uncertainty in perception would infallibly be the result. From all that has been said, we may conclude, that in the external organs of sense, a harmony of action in the two symmetrical parts, or the two similar halves of the organ, is a condition essential to the perfection of sensation.

The external senses are the natural excitants of the brain. The functions of the brain succeed to theirs, and this organ would but languish, were it not to find in them the principle of its activity. From sensation follow perception, memory and imagination; from these the judgment. Now it is easy to prove, that these different functions, commonly known by the name of the internal senses, are governed in their actions by the same laws, which influence the external senses; and that like them, they approach the nearer to perfection in proportion to the degree of harmony existing in the symmetrical parts, in which they have their seat.

Let us suppose for instance one hemisphere of the brain to be better organised, and therefore susceptible of livelier affections than its fellow; in such case the perception of the individual would be confused, for the brain is to the soul what the senses are to the brain; it transmits to the soul the impressions conveyed to it by the senses, as the senses convey to the brain the impressions made upon them by external objects. But, if the defect of harmony in the external senses confuse the perception of the brain, why may not the soul perceive but confusedly, when the two hemispheres of the brain are unequal in power, and incapable of blending into one the double impression, which is made upon them?

The memory is the faculty of re-producing former sensations, the imagination that of creating new ones, now in the act of remembering or imagining, each hemisphere of the brain appears to re-produce, or to create a sensation of its own. If both do not act alike, the perception of the mind, which ought to be the result of the two sensations united, will be inexact and irregular. But, it is evident, that there will be a disparity in the two sensations, if there be a disparity in the two halves of the brain, in which they have arisen, and since the general foundations of the judgment are made up of the faculties of perception, memory, and imagination, if these be confused, the judgment itself must be confused also.

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