Part 7

In general, it appears that the exhalant and absorbent systems are the most universally diffused. Nutrition supposes this; in fact this function is the result of a double movement; one of composition, which brings to the organs, the other of decomposition, that carries from them the nutritive matter; now the exhalants are the agents of the first movement, and the absorbents of the second. As every organ is nourished, and as the mechanism of nutrition is uniform, it follows that these two systems belong to all the organs. After them the cellular system is the most generally found. Where there are no blood vessels, it is sometimes met with, and it always exists where these vessels are. Next to this, the arteries and veins are spread to the greatest number of parts. Oftentimes no nerve is discoverable, where they penetrate, as in the aponeuroses, the fibrous membranes, &c. &c. The nervous is of all the generative systems, that which is found by dissection in the smallest number of parts. The serous membranes, the whole fibrous system, the cartilaginous, the fibro-cartilaginous, the osseous, &c. appear to be deprived of it.

Particularly destined to form a part of the structure of other organs, the generative systems perform the same office for one another; thus the cellular texture enters into the composition of the nerves, and the arteries and veins; and the arteries and veins are ramified in the cellular texture, &c. It is a general intermixture of one with the other.

It may be imagined, from what has now been said, that the generative systems, considered under the relation of organs, forming a common and uniform base for all, ought to be sooner developed than others; and this, observation proves. While there is hardly an outline of the others in the first months of the fœtus, these predominate in a remarkable manner. The nerves, and their centre, which is the brain, the arteries, the veins and their central organ, which is the heart, the cellular texture, the exhalants and the absorbents, exhibit this phenomenon in a striking degree. Mere inspection suffices to prove this in the nervous, arterial, venous and cellular systems; in the other two it is proved by the wonderful activity of absorption and exhalation, at this period of life.

From what has just been said of the general systems of the economy, it is easy to perceive that they perform the most important part of nutrition. They form the nutritive parenchyma of each organ; now I call the nutritive parenchyma, the cellular, vascular and nervous outline of that organ. It is in this outline that the nutritive matter is deposited. This matter being different for each organ, establishes a difference between them. For the bones, it is phosphate of lime and gelatine; it is gelatine alone for the cartilages, tendons, &c.; fibrin for the muscles, albumen for certain other organs; so that if the nutritive parenchyma of a bone was filled with fibrin, it would be a muscle in the form of a bone, and vice versa, a muscle would become a bone with a muscular form, if its parenchyma was filled up with earthy and gelatinous substances. We should know the nature of all the living parts, if their nutritive substances were known to us; but the most of them are unknown, it is chemistry that must enlighten us upon this subject. All the organs resemble each other in their parenchyma, or at least have a great analogy. If it were possible to remove, from all the nutritive matter and leave this parenchyma untouched, we should see only among them, varieties of form, of size, of deposition of cellular layers, of vascular or nervous branches, but not of nature and composition.

In the first period after conception, the mucous mass that represents the fœtus, appears to be only a compound of the general systems. Each organ has as yet only its nutritive parenchyma, the parenchyma upon which nature has imprinted the form of the organ, that is to be developed there. In proportion as this outline is increased, the nutritive substances penetrate it, and then each organ, which until that time had been like the rest in its nature, and forming with them a homogeneous mass, begins to be distinct, and have a separate existence; each one draws from the blood the substance that is proper for it. This addition gives the attributes of thickness, of density, and of nature; but the increase of parenchyma, the augmentation of its dimensions are always antecedent to this. Whilst all inorganic bodies increase by the addition of particles, there is here at first an expansive force, from which length and breadth arise, afterwards substances are exhaled into the parenchyma, which lengthen and widen it.

By what mechanism is it, that each organ draws the materials of its nutrition from the blood, the common source? This depends entirely upon the organic sensibility peculiar to each, which places it in relation to this or that substance and not to another, and which makes it appropriate it to itself, is penetrated by it, and suffers it to enter its vessels on all sides while it draws back and contracts, to prevent what is foreign to it, from being introduced into its texture.

After this substance has continued for some time to form the organ, it then becomes foreign to it and heterogeneous; by remaining longer it would be injurious; it is absorbed and thrown out by the different emunctories; a new substance of the same kind, which is brought by exhalation, takes its place. Each organ is then constantly in a state of composition and decomposition; but this composition and decomposition vary in their proportion. The predominance of the first over the second, constitutes growth. Their equilibrium establishes the stationary state of the body, which is the case with the adult. When the activity of the second is greater than that of the first, then decrease and decrepitude follow.

Such is, in short, the manner in which the general theory of nutrition should be considered, a theory which I shall explain at length in my physiology, and upon which I will now offer a few words, to show that it is not a system formed by accident, but that it rests upon the laws of the economy, and upon its organic phenomena. Now I think that this assertion will be demonstrated, if I prove, 1st. the uniformity of the parenchyma of nutrition; 2d. the variety of the nutritive substances; 3d. the faculty which the parenchyma of nutrition has of appropriating to itself, according to the quantity of its organic sensibility, this or that nutritive substance, to the exclusion of others, of afterwards throwing out this substance, and of taking new. These are in fact the fundamental principles of this theory.

I say in the first place, that the parenchyma of nutrition is the same for all the organs, and that it is an assemblage of red vessels, of exhalants, of absorbents, of cellular texture, and of nerves; these are the proofs. 1st. These different organs are met with in all the others, as I have observed before, anatomy shows them every where, between each fibre, each layer, each point, if I may so say; they are truly the common organs. 2d. When we take away from the organs their different nutritive substances, for example, from the bones the phosphate of lime by acid, and the gelatine by boiling, there is a residue which is evidently cellular and vascular. 3d. There is no doubt but that the mechanism of the union of divided parts is the same as that of their natural nutrition. Now in the healing of wounds, the parenchyma of nutrition is first developed, and is every where the same; every where fleshy points appear, which are cellular and vascular, which have the same appearance and same character, whether they arise from a bone or a cartilage, a muscle, the skin, a ligament, &c. All wounds, in healing, like the organs, resemble each other in their parenchyma; they differ also like the organs, in the nutritive substance that is afterwards deposited in its texture, substances which vary according to the part where the wound happens to be; thus the deposit of the phosphate of lime gives to the callus a different character from that of muscular wounds, which are united by the exhalation of fibrin in the fleshy points that first arise upon the divided surfaces, &c. 4th. The mucous substance which forms the body of the embryo, appears to be nothing but cellular or mucous texture, as Bordeu calls it, which is abundantly supplied with vessels and nerves. In fact, when the organs are developed in this mucous substance, it may be seen in their interstices for a certain length of time, and exhibits there the same appearance as the body of the embryo in the first periods; gradually this substance becomes condensed, is filled with cells, and assumes the form of cellular texture; whence it may be presumed, that in this mucous state of the embryo, there is only the nutritive parenchyma of the organs; and as the parenchyma is the same in all, it is evident that the mass of the embryo must be homogeneous. Nutrition commences, and then each organ appropriates to itself the substance which is proper for it; after this it ceases to be homogeneous. From these considerations, it becomes easy to admit the uniformity of the parenchyma of nutrition, and its cellular, vascular and, in certain cases, nervous texture.

I am aware, that by admitting this common parenchyma of nutrition, it becomes necessary that it should be nourished itself, and consequently that we must go farther back; but in physiology, the art of finding the truth consists, in searching for it in secondary causes; here facts and experiments enlighten our way, beyond that, imagination only is our guide.

After having demonstrated that the organs resemble each other in a common parenchyma of nutrition, it is unnecessary to prove that they differ by the substances that are deposited there. Animal chemistry has within a few years past so much elucidated this point, that it is not worth while to waste time in refuting what has been written upon the identity of the nutritive juice.

In fine, it is easy to conceive, how each parenchyma of nutrition appropriates to itself according to the quantity of organic sensibility it enjoys, the nutritive substances that are proper for it, and which are brought to it by the circulation. It is not a phenomenon peculiar to nutrition; it is observable in all the acts of the organic economy. Thus the secretions take place only in consequence of the determined quantity of this sensibility, which, placing each gland in relation with the fluid that it should separate, makes it receive this fluid, and reject the others; thus the red part of the blood does not ordinarily pass into the exhalants, because the serous part is alone in relation with their organic sensibility; thus the substances that pass the intestines, do not stop in the biliary or pancreatic ducts, although their diameter is sufficient to admit them; thus cantharides are exclusively in relation with the sensibility of the kidneys, mercury with that of the salivary organs, &c. &c.

We see from this, that the mechanism by which the parenchymas of nutrition appropriate to themselves nutritive substances, is not an insulated phenomenon, but a consequence of a general law of organic sensibility. But why has this property as many degrees as there are organs in the economy? Why do these degrees establish relations so different between the organs and the substances that are foreign to them? Let us stop here; let us be contented with proving this fact by a great number of examples, without trying to discover the cause. We could offer nothing but conjectures upon this subject.

These few notions upon the nutritive phenomena, though indirectly connected with the subject of this volume, are not misplaced here; because in these phenomena, the generative systems upon which we are going to treat, perform the greatest part, and because we shall frequently have occasion to refer to them in the examination of the development of the organs, the development that authors have only vaguely examined, upon which the most exact and the most judicious of all physiologists, Haller, has only slightly glanced, but which however ought to receive the particular attention of physicians, of those especially who wish to consider diseases under the essential relation of the influence that age has upon them.

CELLULAR SYSTEM.

This system, which many know still, under the name of the cribriform body, the mucous texture, &c. is an assemblage of filaments, and of white soft layers, intermixed and interwoven in different ways, leaving between them spaces communicating together, more or less irregular, and which serve as a reservoir for the fat and serum. Placed around the organs, the different parts of this system act at the same time as a bond to connect, and as an intermediate body to separate them. Carried into the interior of these same organs, they essentially contribute to their structure.

The great extent of this system, which, though every where spread, is every where continuous, the number of organs it surrounds, and the multiplied relations it presents, do not allow me to describe it, as has been done, in one point of view; in order to give a complete view, it is necessary to separate the different points in which it may be examined.

I shall then at first consider abstractedly the general system, as represented by the continuity of all its parts, in order to consider it in relation to the organs that it surrounds, or to whose composition it concurs. I shall examine it afterwards independently of these organs, as it is spread everywhere in the spaces between them. In fine, its organization, its properties, its relations with other systems, and its development will be the object of my researches.

ARTICLE FIRST.

OF THE CELLULAR SYSTEM CONSIDERED IN RELATION TO THE OTHER ORGANS.

The cellular system, considered in an insulated manner, and in relation to each organ of the animal economy, can be described in two secondary relations. 1st. It forms for each organ a covering, a boundary which is exterior to it. 2d. It enters essentially into the structure of each, and forms one of the essential bases of this structure.

1st. _Of the cellular system upon the exterior of each organ._

The different conformation of the different organs, establishes two very distinct modifications in the relations of the cellular texture, that is exterior to them. In one case in fact, it is contiguous only to one of their surfaces, in the other it envelopes them entirely. The first arrangement takes place, when these organs have one side free, and the other attached, as for example, the skin. The second, which is the most general, is observed, when an organ is attached every where to those in the vicinity of it. Let us describe separately each of these two arrangements.

_Of the cellular system which adheres only to one side of the organs._

There are three membranous organs which are free on one side, and clothed on the other by the cellular texture; these are the skin, and the serous and mucous membranes. We can also consider here, that which covers the exterior of the arteries, the veins, the absorbents and the excretories, which are destitute of it in their interior. As this texture enters also into the structure of these vessels, most authors have examined it, in treating of them. It appears to me more convenient to present under one point of view all the parts of the cellular system.

_Sub-cutaneous cellular texture._

Besides the chorion, into which, as we shall see, a great quantity of cellular texture enters, and which anatomists consider as formed by a particular condensation of this texture, the skin, everywhere that we examine it, presents a subjacent cellular layer, the quantity and density of which vary in the different parts of the body.

Upon the greatest part of the median line, this texture appears more compact, and more adherent to the skin than in many other places. We may be convinced of this, by dissecting upon the middle of the nose, of the lips, of the sternum, upon the linea alba of the abdomen, upon the range of the vertebral and sacral spinous processes, upon the posterior cervical ligament, &c. From this adhesion arises a sort of division of the two great halves of the sub-cutaneous cellular texture; a division that I have sometimes made very evident in my experiments upon emphysema. The air being driven with moderate force under the integuments of one side of the body, diffuses itself gradually, and is stopped in many instances at the median line, so that one side is puffed up and the other exhibits the ordinary state of the cells. It is oftentimes necessary to increase the force very much, in order to overcome the resistance and render the emphysema general. However, we cannot always produce this phenomenon, and sometimes the air spreads immediately every where; this takes place especially if it is forced in about the neck, for the sub-cutaneous texture is as loose there in front, upon the median line, as it is upon the sides.

It is only from the circumstance, that the sub-cutaneous texture immediately under the median line, is somewhat more compact than elsewhere, that we can say with Bordeu, that this texture divides the body perpendicularly into two equal parts. No where, but under the skin, do we see any trace of this separation. Besides, I have demonstrated in one of my works, that the division of the body into two symmetrical parts, is a general attribute of the organs of animal life, an attribute which distinguishes them from those of the internal life, which seem to be characterized by their irregularity; it is under this relation, and not under that of Bordeu, which is contrary to anatomical facts, that the median line should be described.

In the other parts of the body, the sub-cutaneous cellular texture varies considerably. 1st. The density of this texture is remarkable in the hairy scalp, which is with difficulty separated on that account from the aponeuroses and subjacent muscles. Those who have often examined patients who have died of apoplexy, know that sometimes their heads and necks are emphysematous; I have already seen four. Now whilst considerable air is found in the face, little or none is met with under the hairy scalp. 2d. In the face, the sub-cutaneous texture is remarkably loose, it is very abundant there. 3d. Upon the trunk this laxity is also very evident; it accommodates itself to the motions which the great and broad muscles perform there. 4th. Upon the extremities, the sub-cutaneous cellular texture, situated between the aponeuroses and the skin, offers almost every where an equal degree of relaxation. It is only upon the palm of the hand and the sole of the foot that, its texture becoming more compact, the adhesion of the aponeuroses to the skin is more evident, an arrangement that is favourable to the use of these two parts, which are designed to adapt themselves to the forms of external bodies, to grasp and hold them. It is to this compact texture, that must be referred the difficulty that exists of making these parts subject to dropsical effusions. Long after every other part of the sub-cutaneous texture is infiltrated, this preserves its ordinary state. I have seen two patients affected with elephantiasis, where every part of the skin and subjacent texture of the lower extremities was enormously swelled, except the sole of the foot. The contrast of this part, remaining in its natural state, with the top of the foot, which was raised to an enormous swelling, gave that peculiar appearance that all authors have noticed. At the place of the annular ligaments, the sub-cutaneous cellular texture is very compact, and the adhesion of the skin, is also very evident; hence those contractions that are seen in the limbs of infants at the place of the ligaments, the fat penetrating but very little into the cells, that are very closely drawn together.

The sub-cutaneous cellular texture has several different uses. It furnishes the skin with the great mobility it enjoys, a mobility that is particularly observable in the great motions of the trunk and extremities, in the collisions it experiences with external bodies, in the different tumours that get to a great size, as in sarcocele, which is often covered at the expense of a part of the integuments of the penis, the abdomen and the thigh, which are stretched and have a real locomotion.

It is to this texture also, that the organs subjacent to the skin owe in part the facility with which they move in the great contractions of which they are susceptible. The fat contained in great quantity in its cells, contributes to protect the subjacent parts from the impression of the external air. We know, that in general this fluid is more abundant there in winter than in summer, that it is found in a very considerable proportion under the skin of animals that inhabit cold countries, that in consequence of the emaciation that follows great diseases, the impression of the external air is often very sensible, &c.

The serum appears to be in the sub-cutaneous texture, considerably more than in other parts; it has a greater tendency to accumulate there, no doubt on account of its laxity. If we compare the quantity of fluid which enters this texture in a dropsical limb, with that which occupies the intervals between the muscles and the interstices of the fibres of the different subjacent organs, we shall see that it exceeds it considerably, and that the size of the limb is in proportion much more increased by the dilatation of the portion of sub-cutaneous cellular texture, than by that of the portions situated deeper. To be convinced of this, place at the side of a healthy, lower limb, stripped of its integuments and subjacent texture, a dropsical limb prepared in the same manner, and consequently having like the other, only its aponeurotic covering, you will see that the difference is not very great.

_Sub-mucous cellular texture._

The mucous membranes have the same relations with the cellular texture, that the skin has, of which they are a continuation, and with which, as we shall see, they have a great analogy in their structure. There is then a sub-mucous, as well as a sub-cutaneous texture. But there is between them, this essential difference, that the texture of the first is infinitely more compact and condensed than that of the other, and consequently that the adhesion of the mucous system to the neighbouring parts is much greater, than that of the cutaneous system. It is to this difference that may be referred, 1st. the difficulty of dissecting the mucous membranes and of separating them from the subjacent parts. 2d. The impossibility that I have always found in many successive experiments, of producing an artificial emphysema in the sub-mucous texture, whilst I have done it almost every where else, by blowing in air. 3d. The uniform absence of this fluid in this texture, even when the natural emphysemas are the most generally spread. 4th. The equally uniform absence of serum in the sub-mucous cells, in the most general leucophlegmasia; a phenomenon essential to the functions of the hollow organs, which would soon be obliterated, if the sub-mucous texture swelled as much in dropsy as the sub-cutaneous.

Is it to the difference of texture of these two portions of the general cellular system, that must be referred the much greater frequency of phlegmonous inflammation in the second than in the first, or is it that this is less exposed to the exciting causes derived from external bodies? Both circumstances may have an effect. I believe much more readily in the first, as the throat, in which is seated, especially around the amygdalæ, the most lax of all the parts of the sub-mucous texture, is the most frequent seat of phlegmonous inflammation.