In false articulations, old cicatrices of the liver, lungs, &c., we find a substance resembling car tilage ; but its description belongs to " Fibro cartilage," to which we refer.
Chemical composition.—On this subject there is some difference among writers ; Dr. Davy* found diarthrodial cartilage to consist of Albumen 44.5 Water .. 55.0 Phosphate of lime 00-5 100.0 Berzelius professes his ignorance of its corn position. Neither diarthrodial nor non-articular cartilage yielded gelatine, and he doubts." whe ther the mass which constitutes them be of a peculiar nature, or similar to what we find in the fibrous coat of arteries."-t- By boiling costal and synarthrodial cartilages, gelatine is developed. He looks on them to be imperfectly developed bone, and to have the composition of its animal part, with the addition of 3.402 per cent of earth in the false ribs of a man of twenty.
In 100 parts of this earth he gives the fol lowing analysis from Frommherz and Gugert : Carbonate of soda 35.068 Sulphate of soda 24.241 Muriate of soda 8.231 Phosphate of soda 0.925 Sulphate of potass • 1-200 Carbonate of lime .. 18.372 Phosphate of lime .. 4.056 Phosphate of magnesia . 6.908 Oxyde of iron, and loss . 0.999 100.000 Pathological conditions.—Cartilages are not subject to many diseases. Inflammation, ulce ration, and ossification are almost the only ones to which they are liable; and of these the first is very indistinctly marked ; the last scarcely deserves to be called disease. Cartilages are supposed to owe this exemption' from morbid actions to their extremely low degree of vitality. Destitute of red vessels, and supplied with no more nervous influence than is barely sufficient to constitute them a part of the living system, they escape those changes to which highly organized parts are exposed ; and, were it not for their connexion with more delicate and excitable tissues, their exemption would be still more complete. Some eminent pa thologists have gone so far as to consider them incapable of any morbid action ; espe cially the diarthrodial cartilages. " Les carti lages diarthrodiaux ne jouissent point de la vie," says Cruveilhier, who asserts that Ile could not excite disease in them by any of his experiments; and that lie saw them perfectly sound in the midst of every other diseased structure. Mr. Key* also seems to allow them
very little vitality in health, and to consider them very nearly passive in what are called their diseases.
Iylammation is rarely to be met with. Its characters are so slightly marked in diarthro dial cartilage, that we infer its existence, not so much from the signs which are present, as from observing that ulceration is a common occur rence—a state which we suppose to have been preceded by inflammation. The only marks of inflammation to be seen, even when most de veloped, are a softening of the cartilage, and in two instances detailed by Sir B. Brodie, vessels injected with red blood could be traced extend ing from the bones into the cartilages covering them. Severe pain accompanies this disease ; but, as in all the cases on record, ulceration, or some other disease was also present, it cannot be determined how much of the pain belonged exclusively to it. The costal cartilages are subject to painful affections which usually occur in patients who have had syphilis, or to whom mercury has been administered inju diciously. These depend on inflammation of the perichondrium. They may terminate in ulceration or in osseous deposition, and have a close resemblance to periostitis.
Ulceration of cartilage is a very common occurrence in joints, but is extremely rare in other situations. It may be met with at any period of life, or in any articulation, but it is in the hip and knee we most frequently find it, and in persons who have passed the age of puberty and are under thirty or thirty-five. A striking peculiarity attends this affection, namely, that the formation of pus is by no means a constant accompaniment. The form and situations of ulcers in diarthrodial cartilages are very various. Sometimes they are small and deep ; sometimes very superficial, like an abra sion—at one time attacking the free, at another the attached surface; and may commence in the centre or at the circumference. These ulcers may be divided into primary and secondary, the former arising independently of any disease in the adjoining tissues, the latter being preceded by a morbid state of the bone or synovial membrane.