Part 10

The nature of this fluid appears to be essentially albuminous; experiments made upon that of leucophlegmasia show that there is albumen in it; but has not disease then altered its nature? To be satisfied in this respect, I first made a dead animal emphysematous, for the purpose of distending the cells, and to make the alkohol, which I afterwards injected by a syringe, enter them more easily. Some minutes after, the skin having been removed, the subjacent texture presented here and there different whitish flakes. By immersing in diluted nitric acid the cellular portion of the scrotum of a sound body that is dead, or which is better, a portion taken directly from a living animal, we can observe the same thing. It appears, then, that in health as well as disease, the albumen is one of the essential principles of the fluid of the cellular texture. I have taken much of this texture from the scrotum of many bodies, so as to have it separate from the fat, and I have made it boil in about the same time as nearly the same quantity of tendinous substance; at the moment of ebullition, much whitish froth rises upon the water, but little appears in that which contains the tendons.

Is the nature of the cellular fluid the same as that of the lymph that circulates in the absorbents? It cannot be doubted but that these vessels take off this fluid in the cells; it is possible that it is mixed with other substances, those especially that come from nutrition, which alter its nature. Chemical analysis is defective upon this point.

III. _Of the cellular fat._

The fat is the second of the fluids for which the cellular texture serves as a reservoir.

_Natural proportions of the fat._

Very abundant under the skin, around the serous surfaces, the organs of great motions, &c.; it is wanting, as we have said, upon the penis, the prepuce, the scrotum, &c. under the mucous surfaces, around the arteries, the veins, &c. Examined in the interior of the organized systems, the fat varies in quantity. There is none between the interstices of the arterial and venous coats. The lymphatic glands do not appear to contain any. The brain and spinal marrow are destitute of it. It is always found in the intervals of the nervous fibres; it is not often very evident; but in dissecting them, an unctuous substance escapes, which is constant, and which it undoubtedly furnishes. For the most part, it is in considerable quantity in the muscles, especially those of animal life; very little of it is seen in those of organic. In the bones, where there is none, its place is supplied by medullary substance; the cartilages, the fibrous bodies, the fibro-cartilages, are almost entirely destitute of it. The glandular system sometimes has it, as we see it in the parotids, around the pelvis of the kidnies; in other places, as in the liver, the prostate, &c. there is no trace of it. The serous and cutaneous systems are never fatty, although much fat surrounds them. It is the same of the mucous; the epidermis and the hair never have any of this fluid.

From this we perceive that the interior of the organized systems contain in general but very little fat. The different apparatus have but a small proportion between their various parts. It is thus that between the coats of the stomach, the intestines, the bladder, &c. between the periosteum and the bone, between that and the cartilage, between the muscle and the tendon, &c. this fluid is almost always wanting.

It follows from this that it is principally in the interstices, which the different apparatus leave between them, that fat accumulates in cellular reservoirs. Now by examining the different regions, in this point of view, we see, 1st. that upon the head, the cranium and face have an inverse arrangement; that it is very abundant in the second, and wanting in the first, especially in the interior; 2d. that the neck contains a considerable proportion; 3d. that in the thorax we see very little around the lungs, but much about the heart; that upon the exterior of this cavity, the superior part has a considerable quantity around the breasts; 4th. that in the abdomen, it particularly abounds in the posterior part in the neighbourhood of the kidnies, the mesentery, and omentum; 5th. that in the pelvis, there is much of it near the bladder and rectum; 6th. that upon the extremities it is found, like the cellular texture, more abundant above and in the vicinity of the great articulations, &c.

We observe in infancy, that the quantity of fat is in proportion much more considerable under the skin, than any where else, especially that in the abdomen the cellular viscera, the omentum in particular contains but very little at this age. I have established this fact in a great many instances. There are only some flakes of fat around the kidney, frequently these are scarcely visible. All the rest of the abdominal cavity is destitute of it. The pectoral cavity contains scarcely any more, and always much less in proportion than in after life. I have observed also that the intermuscular texture is almost every where deprived of it. We may say, then, that all this fluid is concentrated under the skin, at least while the fœtus is in good health. Does this superabundance of sub-cutaneous fat perform any important office? has it any connexion with the great size of the liver at that period? I know not: it is a phenomenon that should fix the attention of physiologists, especially when it is compared with the absence of fat in almost all the parts where it is afterwards accumulated.

Towards adult age, the abdominal fat is in much greater proportion than the sub-cutaneous. The exterior swelling is as rare towards the fortieth year, as it is common about the fourth and fifth, a period at which all the muscular forms are concealed by the superabundance of fat, and the body is remarkably rounded. Is there any connexion between the large quantity of abdominal fat at the adult period, and the frequency of diseases of which this region is then the seat?

However, the proportions of fat for the different ages are not always the same; there are some exceptions.

In old age almost all the fat is dissolved and disappears; the body is wrinkled, hardened, and becomes thin.

_Unnatural proportions of fat._

Oftentimes the fat accumulates in very great quantity in the cellular texture. I will not cite examples of those enormous collections, of which different authors have given a number of cases; this would be superfluous. I shall only observe, that this state of great corpulency, far from being a sign of health, indicates almost always a weakness of the absorbents which are destined to take off the fat, and has, in this point of view, much greater analogy to serous infiltrations than we commonly think. Different facts establish this assertion. 1st. Every kind of unnatural corpulency is accompanied with a debility of the muscular power, with a state of lassitude and languor of the individual who is the subject of it. 2d. In a man in whom strength and activity predominate, we do not see this fatty enlargement that hides the prominences of the muscles; these are distinctly marked. It is necessary to distinguish carefully the size of the body which arises from cellular fat, from that which is the consequence of the proper development and nutrition of the organs. 3d. Oftentimes the causes which evidently weaken the powers of life, produce a considerable quantity of fat; such as inactivity, rest, great and long continued hemorrhage, convalescence from certain acute diseases, in which the powers still languish, though fat abounds. 4th. A fatty state of the muscles is a state of evident weakness in them. 5th. I have been sometimes convinced, in examining atrophous limbs, that the small size which they retain is owing in part to the fat, which is in proportion almost equal to that of sound limbs, whilst all the other parts, the muscles in particular, are contracted and hardened. 6th. Castration, which takes from the vital powers a part of their activity, from nutrition a part of its energy, is very often marked by excessive corpulency. 7th. On the other hand, as a certain degree of development of the vital powers is necessary for generation, individuals who are too fat, in whom this degree is wanting, are in general not fitted for this function. In woman, this fact is remarkable, it is not less so in man. In other animals we make the same observation. As fowls are fattened for the table, they cease to lay eggs. Most domestic animals are governed by the same law. We should say that there is a constant relation between the secretion of semen and the exhalation of fat, and that these two fluids are in an inverse ratio to each other.

We may conclude from these facts, that if the moderate exhalation of fat indicates strength, its superabundance is almost always a sign of weakness, and that there is in this point of view a kind of connexion between fatty and serous infiltrations, as I have mentioned before. It should be observed, however, that leucophlegmasia almost always arises from an organic disease of some of the viscera, particularly the heart, the lungs, the liver, the womb, and the spleen; hence it is usually incurable, and death is the consequence of the organic disease. On the other hand, an organic disease rarely accompanies corpulency, which does not prevent a long life. If leucophlegmasia arose only from cellular weakness, I am persuaded that it would not disturb the regularity of the functions.

Great fatty collections are oftentimes an effect almost instantaneous of certain circumstances, for example, of atmospheric influence. It is thus that in twenty-four hours, a fog fattens thrushes, ortolans, red-throats, &c. so that they are unable to escape the sportsman. This phenomenon, which is very frequent in autumn, is never so striking in the human species.

The diminution of the fat is as frequent as its increase, and it may be said that there are more cases of extreme emaciation than of remarkable corpulency. The causes which diminish this fluid are these: 1st. long abstinence; the necessary fasting and sleep of dormant animals, furnish us with an example of this; so that in this point of view, fat is the nourishment which is reserved for the time when the ordinary kind is taken away; 2d. every organic disease, continued for a long time, as phthisis, cancer of the pylorus and womb, disorders of the liver, of the heart, &c.; those who are in the habit of examining bodies can judge by the external appearance, without knowing the previous disease, whether the organization of an essential part is changed. In general, in organic affections, there is not only emaciation, but also an alteration in the nutrition of the organs; they are more slender than usual. On the other hand, after an acute fever that has lasted only a few days, emaciation only is observed; nutrition, a function that is deranged as it is exercised, that is to say, slowly, is not yet sensibly affected. There is in this respect a great difference between two bodies equally emaciated; it is sufficient, in most cases, to dissect a limb of each, without seeing the internal viscera, to determine if death has been the gradual effect of an organic disease, or the sudden result of a bilious or putrid fever, &c. To the causes already pointed out, we must add, 3d. every considerable purulent collection, especially if it depends upon a chronic affection; 4th. leucophlegmasia, though we must not believe that fat and serum mutually exclude each other, since we often observe much sub-cutaneous fat in dropsical subjects; 5th. all melancholy affections of the mind which have an influence especially upon the internal life, and which affect the organs of it more particularly than those of external life; 6th. long-continued efforts of the mind, which in a particular manner affect the brain, consequently the first effect is upon animal life, though I have observed that an injury of the functions of this life has less effect upon corpulency than that of the functions of the other; 7th. all evacuations unnaturally increased, as those of the bile, the urine, the saliva, &c.; too frequent emissions of semen, &c. catarrhs, those especially that are seated on large surfaces, as the pulmonary, intestinal, &c.; 8th. long heat of summer, compared with the cold of winter, which is in general favourable to an increase of fat; 9th. running, hard labour, fatigue of every kind; 10th. long diseases, those especially where it is necessary to use only weak aliments, and not being able to continue even these for a long time; 11th. long-continued watchfulness; long sleep producing a contrary effect, that of increasing the fat; 12th. the immoderate use of spirituous liquors, &c. &c.; 13th. the use of acrid and spicy aliments, of those which have opposite properties to the farinaceous, &c. &c.

I do not cite a great number of the causes of emaciation; after these it will be easily perceived what are omitted. I would only remark, that almost all may be referred to two principles, viz. 1st. a general weakness of the powers, a weakness that acts upon the cellular system, as upon all the others, and produces there this phenomenon; 2d. a partial weakness of this system, a weakness arising from the affection of some other organ, whose action seems to increase at the expense of that of the cellular texture.

_Different states of the fat._

The fat is almost always solid and coagulated in dead bodies, but in the living it approaches nearer a liquid state, at least in certain parts, as around the heart, the great vessels, &c. Under the skin it has uniformly more consistence. In many experiments, where I have had occasion to open living animals with red and warm blood, I have never found it exactly flowing as it is when it is melted, though many authors have pretended that it is so, an opinion founded upon the belief that the vital heat would keep it melted. Undoubtedly a degree of heat equal to that of our bodies, acting upon fat out of the body, would make it much more fluid than it is in the living subject. Besides, we know that the temperature is nearly uniform, and that the degrees of the consistence of fat vary remarkably. There is a great difference between that of the omentum, which is among the most fluid of the economy, and that of the neighbourhood of the kidnies, the skin, which is much firmer. Many animals with red and cold blood have liquid fat.

In general, it appears that the nature and state of this fluid are not the same in all the regions; that the fat of the abdomen, thorax and brain differs from each other, though there is no precise rule concerning these differences.

In young animals the fat is white and very consistent after death. It is this consistence that gives to the external covering of the human fœtus, a remarkable firmness and condensation, whilst in the adult the skin of a dead body is flaccid and loose, yields to the least communicated motion on account of the state of the sub-cutaneous fat. This fat in the fœtus is formed into little globules more or less rounded, which give the whole a granulated appearance. Oftentimes it even forms considerable masses; for example there is almost always at this period, between the buccinator, the masseter and the integuments, a ball of fat, which is separate from the surrounding fat, and can be taken out whole. It contributes very much to the remarkable prominence the cheeks have at this period of life.

Fat becomes yellow as we advance in years, and acquires a peculiar smell and taste. In comparing that of veal with that of beef, we readily perceive the difference on our tables. In the dissecting room, this difference is not less remarkable between a subject of ten years and one of sixty.

Instead of fat, we often find around the heart of dropsical and phthisical patients, and of all those who have died of a disease, in which there has been a constant and protracted weakness, a yellowish substance, transparent and fluid, having a gelatinous appearance, and which however, approaches near the character of albumen. This substance also occupies in similar cases other parts; but it is less frequent there. It appears to be gelatinous rather than oily.

_Exhalation of fat._

Different hypotheses have been proposed concerning the manner in which fat is separated from the blood. Malphigi spoke of glands and excretory ducts, which no anatomist since his time has seen and which no one believes in at present. Haller supposed that the fat was completely formed in the arterial system, that it circulated with the blood and floated on its surface on account of its specific levity. This circulating fat then, according to him, escaped through the pores of the arteries, and oozed from all parts into the neighbouring cellular texture. This opinion supposes two things; 1st. the existence of fat ready formed in the arterial system, an existence that is proved by no positive fact, of which I never could convince myself by the examination of red blood as it comes out of the vessels, for if it did exist there would be numerous little drops floating on its surface at the moment it was drawn. In my experiments upon the colouring of the blood, I have frequently established this; I have observed it also in examining the blood of maniacs upon whom arteriotomy has been performed at the Hôtel Dieu. 2d. The opinion of Haller is founded upon a transudation truly mechanical, a transudation that easily takes place in dead bodies, but never in living. In fact, if we lay bare an artery of a living animal, separate it entirely from every thing else, and examine it ever so long, we shall discover no oozing of fat through its coats, though the blood circulates in it as usual. There is an infinity of arteries, spread in the cellular texture, through which fat never transudes, as we see in the scrotum, the eyelids, &c.; now in these places the arteries are organized as elsewhere, and they ought therefore to have the fat ready formed in the blood that they circulate; then, according to Haller, fat would be deposited there. Besides, we shall see under the article upon exhalations, that this transudation through the pores of the arteries, whatever fluid is supposed to be transuded is evidently repugnant to the laws of the animal economy. I refer then to this article, to establish the fallacy of Haller's opinion; under that article we shall see also, that the fat is separated by an exhalation analogous to that of all other exhaled fluids, that is to say, by the vessels of a particular order, which are intermediate between the extremities of the arteries and the cellular texture. Some authors have thought that they saw the vessels that carry the fat, and have designated them under the name of adipose; but it appears, that like the other exhalants, they are invisible and can only be proved by a train of reasoning, which however, satisfactorily establishes their existence. We can apply to the exhalants of fat, what will be said upon the exhalant system in general.

I will not treat of the chemical nature of fat, of the acid it contains, of the particular alterations it undergoes under different circumstances, that for example, that it experiences when animal substances that contain it, such as the skin, the muscles, &c. are for a long time macerated in water. This would lead me into details foreign to this work. Besides, I could add nothing to what modern chemists have said upon this subject.

I will terminate this article with an important remark; it is this, that in those parts which nature has deprived of fat, it would have injured their functions. The penis increased in size by it, would not have had a proper relation to the vagina. The eyelids loaded with fat could scarcely be raised. Accumulated in the sub-mucous texture, it would have contracted the cavity of the organs which the mucous surfaces line. Spread in that which surrounds the arteries, the veins and the excretories, it would have obstructed the caliber of these vessels; and here observe, that its uniform absence in the sub-arterial texture is a proof against the opinion of Haller upon its transudation. Accumulated in the cerebral cavity, it would have compressed the brain on account of the resistance of the bony parietes of the cranium, &c. which do not yield like those of the abdomen, when the gastric viscera are loaded with fat. In the thorax, the diaphragm can descend, and the lungs can without danger occupy less space when there is considerable fat exhaled in the mediastinum. This remark, applicable also to the serum, explains an important phenomenon in diseases, viz. that a very small quantity of fluid poured out upon the tunica arachnoides can disturb the functions of the brain, whilst a great effusion is unattended with danger in the abdomen or the thorax.

ARTICLE FOURTH.

ORGANIZATION OF THE CELLULAR SYSTEM.

The cellular system, like almost all the others, is composed of a peculiar texture and of common parts.

I. _Of the texture peculiar to the organization of the cellular system._

Much has been written upon the nature of this texture; Bordeu has given some vague ideas upon it, but no experiments. Fontana has made researches which lead but to few results, upon its intimate structure and upon the tortuous cylinders of which, according to him, it is an assemblage. Let us throw aside all hypotheses that examination does not support; let us follow nature in the phenomena of structure that she shows us, and not in those she wishes to conceal. In thus considering the cellular texture, we see that it is very different from a species of glue, with which some have wished to compare it. It is an assemblage of many whitish filaments, crossing very often certain kinds of delicate layers, which form cells with these filaments. To see this organization well, a piece of the cellular portion of the scrotum should be taken, which has no fat, and whose texture is consequently not concealed by this fluid; this portion being stretched into a kind of membrane, is seen very distinctly. Then there may be plainly distinguished, 1st. a transparent net-work, arranged in layers, which makes the foundation, if we may so say, and the tenuity of which is such, that it has been aptly compared by a physiologist, to the soap bubbles that are thrown into the air with a pipe. It is impossible to distinguish, by the naked eye, any fibre in the texture of these layers; every thing is there uniform. 2d. They are very evidently crossed by numerous filaments, which running in all directions, are interwoven in every way, all of which touch, when the cellular texture is pressed together, but when stretched out, there can be seen between them the layers of which I have just spoken. The more it is extended, the larger consequently the membrane becomes, the interstices between the filaments are greater, and the intermediate layers are also more apparent.

What is the nature of these filaments? I presume that some are absorbents, others exhalants, and that many are formed in the places where the layers unite together for the formation of the cells. As the thickness arising from this union is greater, they are distinguished by more evident lines upon the cellular texture stretched into a membrane. What induces me to believe this, is, that when, instead of examining the cellular texture upon a portion taken from the scrotum, and stretched as I have described, it is observed in an artificial emphysema, as in that of the slaughter-houses for example, then there is seen upon the covering of each cell, only the non-filamentous layers of which I have spoken, without any of those filaments that were seen crossing it in the other method.