I may add, that in my own examinations of pure cartilage, from the skeletons of cartila ginous fishes, and from the human subject, I have found the foregoing descriptions correct. The cartilaginous corpuscles may be always seen under the compound microscope, with an object glass of a quarter of an inch or an eighth of an inch focus.
In man and the mammalia, the following structures may be enumerated as belonging to the class of fibro-cartilages : 1. The so-called inter-articular cartilages in the knee, sterno clavicular, and temporo-maxillary joints; that in the wrist joint seems to me to be purely cartilaginous. 2. The fibro-cartilages of cir cumference, as in the hip and shoulder-joints. 3. The fibro-cartilages of tendons, which ulti timately form sesamoid bones, and those of tendinous sheaths. 4. According to Miescher, the tarsal cartilages. 5. The inter-osseous lamina:, as those between the pubes, pieces of the sacrum and coccyx, and, in a modified form, the intervertebral substance.
In the inferior vertebrata and in the inver tebrata fibro-cartilage gradually disappears : in the former, the intervertebral substance seems to be the only remnant of it, excepting perhaps the sclerotic coat of the eye in some fishes. In the invertebrata, Blainville considers the three tubercular teeth of the leech as being fibro-cartilaginous.
Morbid conditions of fibro-cartilage.—As fibro-cartilage in its physical and vital pro perties so nearly approaches pure cartilage, it is reasonable to expect a great similarity in the phenomena of disease as they are manifested in the two tissues. Fibro-cartilage appears to he susceptible of reparation in the same man ner as pure cartilage. (See CARTILAGE.) A substance bearing some resemblance to fibro cartilage sometimes forms the connecting me dium between the fractured portions of a bone, where bony union cannot be obtained.
The phenomena of inflammation and ulce ration in fibro-cartilages are very similar to those in pure cartilage : in the joints these morbid changes are generally complicated with similar diseased conditions of the other tex tures, either cartilages or bones, whence they are propagated to the fibro-cartilages. It is well known that a condition of the interverte bral discs, which is commonly spoken of under the name of ulceration, is frequently coin cident with caries of the vertebra', having in some instances preceded the vertebral disease, and in others followed it. To Sir Benjamin Brodie we are indebted for the observation that the diseased state of the intervertebral substance has sometimes the precedence of that of the bones; in one case, related by him, where ulceration of the articular cartilages had begun in several other parts, those between the bodies of some of the dorsal vertehrw were found to have been very much altered from their natural structure. Ile adds, " I had an opportunity
of noticing a similar morbid condition of two of the intervertebral cartilages in a patient who, some time after having received a blow on the loins, was affected with such symptoms as in duced Mr. Keate to consider this case as one of incipient caries of the spine, and to treat it, accordingly, with caustic issues; and who under these circumstances died of another complaint. Opportunities of examining the morbid appearances in this very early stage of disease in the spine are of very rare oclur rence, but they are sufficiently frequent when the disease has made a greater progress; and in such cases I have, in some instances, found the iotervertebral cartilages in a state of ulce ration while the bones were either in a perfectly healthy state, or merely affected with chronic inflammation, without having lost their natural texture and hardness." Otto mentions that he has several times satisfied himself that the destruction of the spine may originally spring from the intervertebral substance; but he has never found suppuration, unless when at the same time the bones and neighbouring cellular tissue were inflamed4- The anatomical cha racters of this condition to which we have been alluding consist in an erosion and soften ing of the fibro-cartilage, frequently attended with the effusion on the surface of a dirty puriform and often fetid fluid.
Fibro-cartilage is not prone to become ossi fied; in very old subjects the superficial portion of the intervertebral substances is often ossi fied, but this is an extension of ossification from the bone or from the anterior common ligament : it is very rare to find any of the inter-articular fibro-cartilages ossified. The ossification of the interpubic fibro-cartilage in advanced age seems to be of a similar nature to that of the intervertebral substances.
Masses of a substance very similar to fibro cartilage are sometimes met with accidentally developed ; we lind them in or connected with the uterus, in tumours, and in serous or sy novial membranes.
(R. B. Todd.)