Part 5

Gangrene once taken place, is everywhere the same, since it is only the absence of life, and all dead organs have the same properties. But according to the sum of organic sensibility which each system has, it is more or less disposed to die after inflammation, in the midst of others which retain their life. Who does not know that the carbuncle which soon kills the part it seizes, only attacks certain systems; that the osseous, the cartilaginous, the nervous, &c. are always exempt from it?

The essential fault of every medical doctrine is that of considering diseases too abstractedly; they are so modified in each system, that their aspect is wholly different. If I may be allowed the expression, it is always the same individual, but in entering each system, it has a different appearance there, so that often you cannot recognize it. When will medicine be so far advanced that the treatment will correspond with these varieties? There should certainly be a general treatment of inflammation; but it should be modified differently, according as we apply it to phlegmon, erysipelas, catarrh, &c.

This then is a very evident proof of that peculiar character which inflammation takes in each part. We know with what ease and rapidity the blood flows to any part of the skin in consequence of irritation there; prick or rub briskly a part of this organ, it reddens in a moment. This takes place also, though less sensibly, on the mucous surfaces. This is not equally seen upon the serous; I have frequently ascertained this on living animals, when I have laid bare these surfaces and irritated them in different ways. The afflux of the blood does not immediately follow the irritation: there is always an interval between one and the other, never less than an hour.

VII. Structure, and Properties of the Capillaries.

What is the structure of the capillaries? So great is their tenuity that we evidently cannot have upon this point, any kind of data founded upon experiment and observation. Only it is very probable, it is even certain, that this structure is modified differently in each organ, that it is not the same in the tendons, the aponeuroses, the muscles, &c. that it really partakes of the nature of the organ of which it makes an integral part.

The membrane which lines the excretories, the arteries, the veins, the exhalants, vessels which go into the system of the capillaries or come out of it, is very like that of these capillaries; but it is not certainly the same.

It is the diversity in the structure of the capillaries, according to the organs in which they are found, which has an essential influence upon the difference which the vital properties exhibit, particularly the organic sensibility and the insensible organic contractility in each system in which we examine them; hence peculiar modifications in all those diseases over which these properties preside, and which are seated especially in the capillaries, such as inflammations, tumours, hemorrhages, &c. &c.

The difference in structure of the capillary system, sometimes becomes manifest to the eye. Thus the spleen, the corpus cavernosum, instead of presenting, like the serous surfaces, a vascular net-work in which the blood oscillates in different directions, according to the motion it receives, exhibit only spongy, cancellated textures, whose nature is but little known, in which the blood appears often to stagnate, instead of moving, &c.

VIII. Of the Circulation of the Capillaries.

The circulatory phenomena are of two kinds in the capillary system: 1st, there is the motion of the fluids; 2d, the alterations which they undergo.

Motion of the Fluids in the Capillary System.

These fluids are, 1st, the blood; 2d, others differing from it in their composition, though we only know their differences of appearance. Let us examine the laws of the motion of each kind.

The blood, after it has entered the capillary system, is evidently beyond the influence of the heart, and only circulates by that of the tonic forces, or the insensible contractility of the part. If we examine the phenomena of this capillary system but little, we shall be easily convinced of this truth, which Bordeu first taught. The capillary system is really the boundary, beyond which the influence of the heart does not extend. Hence why all the vessels that go out of this system, exhibit in the fluid they contain a motion that does not correspond with that of the arteries that go to it. 1st. After what we have said, there is no doubt of this, as it regards the veins. 2d. It is also true as it respects the excretories. The increase of secretions does not correspond with the increase of the action of the heart, nor does their diminution with the diminution of the pulsations. Who does not know, on the contrary, that often in a violent paroxysm of fever, in which the agitation of the arterial blood is very great, all the glands seem to shut up their ducts and not to pour out any fluid? 3d. It is the same with all the exhalations; it is not when a fever is the greatest, that we sweat the most, but when it is somewhat diminished. Hemorrhages are evidently but an exhalation; now who does not know, that the pulse is often very weak, when the blood flows abundantly from the mucous surfaces of the womb, the nostrils, the bronchia, &c.? Who does not know on the contrary that in extreme agitations of the heart, most often the blood does not flow by the exhalants? Is the quickness of the pulse increased during menstruation? It is the redness of the capillary system, the abundance of the blood of this system, which is often, as I have said, the forerunner of active hemorrhages; but it is never the increase of the action of the heart. Oftentimes fungous tumours, soft flesh that shoots up in wounds of a bad nature, polypi, &c. pour out blood; the heart has nothing to do with these hemorrhages, they come evidently from the capillary system. Who does not know, that frequently when the exhalants pour out copiously serous fluids upon the membrane of that name, in the production of dropsies, the heart is, like all the other parts, in a state of real inertia?

Since then all the vessels going from the capillary system exhibit in their motions no sort of harmony with those of the heart, it is evident that the influence of this organ is interrupted, is terminated at the capillary system.

Observe nutrition; it is clearly the capillary system that distributes everywhere the materials that it has received by the impulse of the heart; now the influence of this does not extend to the place where the nutritive matter is deposited. In fact, its impulse everywhere equal and uniform, pushes the blood with nearly an equal force to all parts, with some exceptions in the fœtus. Now nutrition is on the contrary extremely unequal; at one age, it is one part that takes more increase, consequently receives more nutritive matter; at another age, it is another organ. This inequality, is the first and principal phenomenon of growth.

How can we reconcile with the sole and uniform impulse of the heart in all parts, inflammation, the production of herpes, of different eruptions, &c. which appear in some places? Would inflammation exhibit so many aspects, according to the system it seizes, if the heart alone presided over its development? All the difference between catarrh, erysipelas, phlegmon, &c. would disappear; and there would be only what arose from being nearer, or further from the heart.

Let us cease then to consider this organ as the sole agent which presides over the motion of the great vessels and the small, which, in these last, driving the blood abundantly to a part, produces there inflammation, which by its impulse causes the different cutaneous eruptions, secretions, exhalations, &c. The whole doctrine of the mechanicians rested, as we know, upon the great extent which they gave to the movements of the heart.

There are evidently two kinds of diseases in relation to the circulation; 1st, those that affect the general; 2d, those that affect the capillary circulation. Different fevers form especially the first kind. Different eruptions, tumours, inflammations, &c. produce the second; now, though many relations connect the second with the first, it is not essentially dependant upon it; the following is the proof of this; fevers can evidently only exist in animals with great vessels, in those in which the fluids move in a mass; they cannot take place in zoophytes and plants, which have only a capillary circulation; yet these last classes of animals and all vegetables are subject to all the affections that disturb the capillary circulation. Thus we see upon plants many tumours; their wounds unite; two portions even contract adhesions, as a graft proves. The diseases of their capillary system are no doubt different from those of animals in their progress and their nature; but they exhibit always the same general character, because they are derived from the same properties, organic sensibility and insensible contractility.

Since the diseases of the capillary system are not essentially connected with those of the general vascular system, they are not then dependant on it; the circulation of the first is but indirectly subordinate to that of the second. Hence why the two circulations can be separate; why more than half of the organized beings have only the capillary. This is the most important, since it immediately pours out the materials of nutrition, of exhalations, of absorption: thus it exists in all organized beings. We cannot conceive of any one without it, because we cannot conceive of any one that is not continually composed and decomposed by nutrition.

From what we have thus far said, it is evident, that the blood after it has arrived in the capillary system, is moved there only by the tonic influence of the solids; now, as the least cause alters and changes their properties, it is subject there to an infinity of irregular motions. The least irritation makes it recede, advance, deviate to the right, or the left, &c. In the ordinary state, it moves generally in an uniform manner from the arteries towards the veins; but at every instant it may find causes of irregular oscillations in its innumerable anastomoses; hence, as we have seen, the necessity of these anastomoses. These irregular oscillations in the motion of the blood in the capillary system, can be seen with a microscope. Haller, Spallanzani and others, whose experiments are too well known for me to relate them here, saw them a hundred times. They saw the globules advance, recede, move in many different directions in animals with red and cold blood, when they irritated the mesentery or any other transparent part. In animals with red and warm blood, in those even whose mesentery is almost as transparent as that of the frog, as in the guinea-pig, it has appeared to me infinitely more difficult to trace the motion of the blood in the capillaries.

It is easy to see that all the phenomena of inflammation, of different eruptions, of tumours, &c. are especially founded upon this susceptibility of the blood, in the capillary system, to move in an infinite variety of directions, wherever irritation calls it.

From what has been said, it is evident that there are times when the blood passes with less rapidity through the capillary system, and there are others, when it moves more quickly. How then is the relation always preserved the same, between the arterial and the venous blood? It is in this way; the irregular oscillations hardly ever take place except in one part of the capillary system; in no case is the whole of it affected; thus if the blood moves more slowly in the cutaneous capillary system, its velocity is increased in the cellular, the muscular, &c.

This is in fact an invariable law in the vital forces, that if on the one hand they increase in energy, on the other, they diminish; we might say, that there was only a certain quantity in the animal economy, that this might be divided in different proportions, but it cannot be increased or diminished. This principle results so evidently from all the phenomena of the economy, that I think it unnecessary to support it by numerous proofs; now, taking this as incontrovertible, it is evident that one portion of the capillary system increasing its action, only at the expense of the others, the sum total of blood transmitted from the arteries to the veins remains always nearly the same. All the systems are then, in this respect, supporters of each other; if nothing passes by the capillaries of one, it is the same thing, provided the capillaries of another transmit double the amount of fluid that they do in an ordinary state.

Observe the blood in the cutaneous capillaries before the paroxysm of intermittent fevers; it recedes from these capillaries; all the surfaces that it reddened, become pale; the capillaries of the other systems supply the momentary defect of the action of these. Who knows if, in many cases where the skin becomes very red, when much blood enters it, there is not in the other systems a paleness analogous to that of the skin during the cold fit of fever? I not only think this very probable, but I have no doubt of it. The external capillaries certainly contain more blood in summer, whilst those of the internal systems receive more in winter. There is then continual varieties in the mode of the passage of this fluid through the general capillary system; each system transmits by turns, more or less, according as it is affected.

When we see the glands, frequently in a short time pour out an enormous quantity of fluid, the serous, cutaneous, mucous exhalants, &c. furnish also much greater proportions than in a natural state, we are astonished that the circulation can at the same time continue with the same regularity; we are not less so undoubtedly, when we see on the contrary all the evacuations suppressed, and nothing goes out from the animal solids; now in all these cases, it is the capillary system, whose forces differently modified in the different parts, re-establishes the general equilibrium which would inevitably be lost, if the heart was the agent of impulse which pushed to the extremities the secreted and exhaled fluids, and transmitted the black blood to the veins.

Sometimes however a derangement almost universal takes place in the capillary system, especially on the exterior; this takes place in sudden changes of the air. Though the vital laws preside essentially over the capillary circulation, yet the degree of pressure of the surrounding air can modify it to a certain point; we have a proof of this in cupping glasses, or in any other means that produce suddenly a vacuum upon a part of the body; then the fluids pressed in the neighbourhood by the external air, and not compressed on the contrary at the place of the cupping glass, raise up and distend considerably the skin. The sudden changes of the atmosphere produce upon the whole body, though in a less degree, the effect of a cupping glass. If the air is rarefied, the whole external capillary system is more full; even the sub-cutaneous veins swell; a very considerable part of the blood experiences then a derangement in its motion, between the two systems with red and black blood. The harmony, the correspondence of these two systems is disturbed; hence the uneasiness, the sense of weight, &c. of which we are instantly relieved by a sudden change of the atmosphere.

The evacuation of the blood also establishes differences, though less, in the capillary system. Bleeding is of two kinds; one lessens the blood of the circulation of the great trunks; and then it is sometimes red, as in arteriotomy; but most often it is the black, that is drawn off; the other takes blood from the capillary circulation; this is done by leeches, cupping, &c. Each produces a different change in the course of the blood. Physicians formerly were desirous of knowing from which vein they ought to bleed. I think it is much more important to know when we should by bleeding, act upon the general circulation, and when upon the capillary. In many local congestions, I do not think that you can diminish the quantity of blood in a part of the capillary system, by diminishing the mass of this fluid in the great trunks; you might take a quarter at least of the blood that there then was in the economy, if the part is irritated, the blood will still flow as much to this part. On the contrary, you may double by transfusion, the mass of this fluid in an animal, local inflammations will not arise, because there must be a preliminary irritation before the blood flows towards, and enters a particular part of the capillary system.

The fluids differing from the blood which circulate in the capillary system, 1st. are evidently like it beyond the influence of the heart. 2d. The influence of the tonic powers presides over their motions. 3d. They are consequently subject to irregular oscillations, according as the capillaries are differently affected.