III. Vital Properties.
The vital properties are also very obscure in them. There is no animal sensibility in the natural state; it is only when inflammation or some other cause raises their organic sensibility, a sensibility which their functions necessarily suppose, it is only then, I say, that the brain perceives painfully the different irritations of which these organs are the seat. This becomes manifest, especially when foreign bodies are formed in the articulations, which suffer from their presence or are insensible to them, according as they irritate or not by their position, the cartilaginous extremities. There is neither animal nor sensible organic contractility in the cartilages; the insensible organic or tone alone exists in them, and this not in a great degree.
The sympathies are obscure, almost wanting in the cartilaginous system. I do not know that in the acute affections of the different organs, we observe sympathetic phenomena of sensibility or contractility in them. They remain tranquil in the midst of the general derangement which affects the other systems in this sort of diseases. In chronic affections even, they experience but little alteration; examine, for example, comparatively, the body of a man that has died a violent death, which has left his organs untouched, and that of one who has died from phthisis, dropsy, cancer, &c. you will perceive between almost all their organs a striking difference; the aspect of the muscles, of the mucous and serous surfaces, of the vessels, the nerves, &c. is entirely changed by the slow alteration they have undergone in the second; in the midst of these alterations the cartilages are unchanged, their appearance is almost the same as in a natural state.
Character of the Vital Properties.
From what has been said, it is evident that the cartilaginous life can have but little activity, that all the morbid phenomena must be characterized in these organs by a peculiar slowness, and that inflammation, for example, must always have in the cartilages, as in the bones, a chronic progress; this is rendered very clear by the following experiment. Lay bare a cartilage, divide it, and afterwards bring it in contact with a portion of a muscle, the skin, &c. also divided at their surface; the reunion does not take place, or at least not until a very long time. Why? because the life of the muscle or the skin being much more active than that of the cartilages, the inflammation of the first organs will be much more rapid than that of the second, and consequently the first inflammatory period of one will correspond to the last of the others. Now the reunion is so much the easier as the inflammatory periods correspond the more exactly in the two divided parts that are in contact. Hence why two parts of the same organ unite much more easily than two surfaces belonging to different organs. Hence why the greater the analogy in the lives of the two organs, the greater the facility with which they unite; why the difficulties increase as the differences of life become greater. Two osseous surfaces in contact require thirty or forty days to unite; the two edges of a cutaneous wound unite in two or three days. If you attempt to render continuous two organs thus unlike in their mode of cicatrization, by putting them in contact, you will succeed but slowly. Cover with skin the osseous extremity of an amputated stump; this will be in a state of suppuration, before the bone has hardly begun to soften; thus good practitioners have abandoned these pretended unions by the first intention, so much boasted of, after amputation by the flap operation. These unions would no doubt take place, if the life of the organs which enter into the composition of the flap was the same. But with the diversity of these muscular, osseous, tendinous, cellular, nervous organs, &c. it requires a long time for all their lives to be placed as it were in equilibrium, and for these organs to agglutinate at their divided extremities. I have already observed that the division of inflammations into acute and chronic gives physicians an inexact idea; for the duration of the inflammatory phenomena in the organs is wholly relative to their degree of life. An inflammation of the cellular texture and of the skin is acute, when it lasts but a few days; it is chronic when it continues forty or fifty days; in a cartilage, this last period may be that of an acute inflammation, whilst a duration of many months is necessary to make it chronic, as the diseases of the joints exhibit frequent examples.
The natural functions, as well as the morbid affections, have this slowness of the vital phenomena of the cartilages. The constant composition and decomposition, which their nutrition supposes, is not rapid. It requires a long time for nutritive substances to combine with them. I am persuaded that in animals which die suddenly from the effects of a carbuncle and whose muscles, glands, membranes, &c. almost instantly penetrated with the deleterious principles by the nutritive motion of composition, present an aliment so injurious, I am persuaded, I say, that these injurious principles not yet having penetrated the cartilages, these might be digested without danger. It is to the slowness of the motion of decomposition that must be attributed the slowness of the resolution of cartilaginous swellings; for tumours are resolved by the same laws that decompose our organs, as they are formed by the same laws that preside over their composition.
The cartilages and the analogous organs, are to the other parts of the economy, as it respects their vitality, what the zoophytes and other animals with a capillary circulation only, are to the animals better organized, to those with a general circulation and those that have a heart with a double ventricle. As much as life considered in general in the series of beings that it animates, presents a difference in its activity, so much it differs in the same respect, examined in particular in the organs of each of these beings.
ARTICLE FOURTH.
DEVELOPMENT OF THE CARTILAGINOUS SYSTEM.
The osseous and cartilaginous systems are confounded in the embryo; as the first is developed, the second contracts; the latter very evidently has gelatine for its principal base; I shall not return to the proofs that have demonstrated it in the osseous system.