III. Vital Properties.
There is never in the fibrous system animal contractility, nor sensible organic contractility. Organic sensibility and insensible organic contractility are found there as in all the other organs.
The animal sensibility exists in it in the natural state; but it appears in a peculiar way, of which no system in the economy, I believe, offers an example and which no one has precisely pointed out. The ordinary agents that put it in action, such as the different stimulants, mechanical, chemical, &c. cannot develop it here, unless the organ is in an inflammatory state. The tendons, the aponeuroses, the fibrous membranes, the ligaments, &c. laid bare in operations, in experiments upon living animals and irritated in various ways do not occasion any pain. What has been written on the sensibility of the periosteum, the dura-mater, &c. taken in this sense is evidently contrary to observation. But if the fibrous organs are exposed to a sudden and violent extension, then the animal sensibility is evident in it to the greatest degree; this fact is particularly remarkable in the ligaments, the fibrous capsules, the aponeuroses, &c.
Lay bare an articulation in a dog, that of the leg, for example; dissect carefully the organs that surround it; remove the nerves especially, so as to leave nothing but the ligaments; irritate these with a chemical or mechanical agent; the animal remains unmoved and gives no sign of pain. Then stretch these ligaments, by twisting the articulation, the animal in an instant throws himself down, is convulsed, cries out, &c. Finally cut these ligaments so as to leave only the synovial membrane which exists here without the fibrous capsule, and twist these two bones in an opposite direction; the twisting ceases to be painful. The aponeuroses, the tendons even laid bare and drawn in an opposite direction, produce the same phenomenon. I have frequently repeated these experiments which prove incontestably what I have advanced, viz. that the animal sensibility of the fibrous system, incapable of being brought into action by the ordinary means, is very evident in the distensions of which they are the seat. Observe that this manner of being excited is analogous to the functions that it performs. Separated in fact by its deep position from every external excitement which can act upon it chemically or mechanically, it has no need, like the cutaneous system for example, of a sensibility which would transmit the impression of it; on the contrary, the most of these organs, as the ligaments, the fibrous capsules, the tendons, &c. being very subject to being distended, stretched and twisted in the violent motions of the limbs, it was necessary that they should communicate to the brain this kind of irritation, the excess of which might without this become injurious to the articulations or the limbs. Observe how nature accommodates the animal sensibility of each organ to the different excitements it may experience, to those especially which would become dangerous if the mind was not informed of them; for this vital power is the essential agent by which the animal watches over its preservation.
It is to this sort of sensibility of the fibrous system that must be principally attributed, 1st, the acute pains that attend the production of luxations; 2d, those more severe ones which patients experience in the extensions necessary to reduce them, especially when, as in those of long standing, we are obliged to employ considerable force; 3d, the intolerable suffering of the punishment that consisted in drawing a criminal with four horses; 4th, the painful sensation which arises from twisting, which is occasioned by a stretching of the spinal column and consequently of its ligaments, by turning the head too quickly, &c.; 5th, the acute pain that those experience immediately before the accident who break a tendon, a pain which ceases in part when the rupture takes place; 6th, that less sensible pain which we feel when any tendon, the tendo Achillis for example, is from a bad position too much stretched; 7th, the great increase of pain that is experienced, when a swelling exists under an aponeurosis, which being unable to yield, is very powerfully raised; 8th, the painful sensation we feel in the ham when we wish to force the extension of the leg, by which we stretch the two oblique ligaments destined to confine this extension, &c. &c.
It is without doubt to the insensibility of the fibrous organs to one kind of excitement, and their sensibility to another, that must be referred the contradictory results of the experiments of Haller on the one part, and those of his antagonists on the other, upon the dura-mater.
Character of the Vital Properties.
The vital activity is much greater in the fibrous, than in the osseous and cartilaginous systems. This is proved very evidently, 1st, by the degree of animal sensibility which we have just observed in it, and which is foreign to the other two systems; 2d, by the much greater disposition of this system to become the seat of pains more or less frequent, and especially of inflammation, &c.; 3d, by the much more acute character that this affection has in it, as we see in acute rheumatism, which principally affects the fibrous parts of the great articulations of the axilla, the hip, the knee, the elbow, &c. the aponeurotic part of muscles, &c.; 4th, moreover, by the great mobility of rheumatic pains, which go with astonishing quickness from one place to another, which consequently suppose a great quickness in the alteration of the vital forces of the different parts of this system; 5th, by the greater rapidity of its cicatrization; thus by laying bare fractures made for the purpose in animals, I have constantly observed that the fleshy granulations coming from the periosteum and the medullary organ, are all formed, whilst those furnished by the bone itself have hardly commenced. I would observe in regard to this cicatrization, that the parts of the fibrous system in which the greatest number of blood vessels enter, as the periosteum, the fibrous membranes, the capsules, &c. are the most capable of this phenomenon, which takes place with much more difficulty in those where little or scarcely any blood goes, as in the tendons, the ends of which are very slow in uniting; 6th, we may finally be convinced of the difference of vitality of the fibrous system and that of the preceding ones, by the progress of an exostosis compared with that of periostosis, or a swelling of the dura-mater, &c. Yet there is still in respect to the vitality a remarkable slowness in this system. We see it especially in certain affections of the limbs, in which gangrene takes place, and makes, like the inflammation that precedes it, rapid progress in the cellular texture, the muscles, &c. whilst that, as I have said, the tendons that have been laid bare do not alter until some time after, and are remarkable for their whiteness in the midst of the general blackness or lividity.
The fibrous system presents a remarkable phenomenon; it is that it hardly ever contributes to the formation of pus. I do not know that after inflammations of this system, purulent collections have been ever observed. Rheumatism, which is ranked with the phlegmasiæ, is never accompanied by these collections; some gelatinous extravasations only have been found around the tendons. That which was formerly taken for a suppuration of the dura-mater in wounds of the head, is very evidently a purulent oozing from the arachnoides, analogous to that of all the other serous membranes. Why does this system refuse, or produce pus with so much difficulty, or why is it not as much disposed to do it as most of the other systems? I know not. Nor do I know that in the midst of the cartilages collections of this fluid have been found. The inflammations of the cartilaginous system are remarkable, because they rarely or never terminate by suppuration.