Loose cartilages.— The cavities of the serous and synovial membranes sometimeg contain morbid products in the shape of certain free or unattached substances, which, from their usual appearance and consistence, are best known as " loose cartilages." The most frequent situation of these bodies is in the knee-joint, and next to this, in the synovial sheaths of the flexors and extensors of the hand or foot ; but they are not uncommonly found in the subcutaneous bursx over the patella, trochanter, or acromion. More rarely they are seen in connection with the serous membranes; for instance, in the tunica va ginalis testis, or in hernial sacs. They may also exist in the diarthrodial species of false joints.
Their appearances offer great variety in different cases. In some instances, as often happens in the knee-joint, only one, or per chance two such bodies are present. Here they are of considerable size, attaining the magnitude of a large bean or alinond ; their shape is a more or less flattened oval, and their surface is smooth and slippery. Their consistence is firm and elastic, their appear ance whitish and cartilaginous, their substance uniform and structureless.
When comparatively recent, or of only a few weeks' or months' standing, they may vary somewhat front this description by the possession of a rough surface on one side, which indicates the seat of their previous attachment to one of the bones of the leg. The observations of Cruveilhier * have furnished us with a knowledge of the stage which, at least in some instances, immediately precedes this condition. He has shown that, in some cases, the development of these bodies occurs in the subserous or rather subsynovial tissue ; that their enlargement carries forward the synovial membrane ; and that a peduncle is thus formed, the rupture of which sets them free, in the articular cavity.
There are other cases which possibly re present a different class, and which are dis tinguished from these by the characteristics of the greater number, lesser size, and, for the most part, much softer consistence of these bodies. Their general features have long been known to anatomists, and recently the minute descriptions of Biddert and Hyatt have added itnportant, though appa rently conflicting, details concerning them.
In the case which Bidder has narrated, the rnorbid product was removed from the knee-joint during the life of the patient, so that the appearances of the synovial mem brane are necessarily wanting. The mass consisted of granules, the shape of which was always a flattened oval ; and their size offered a similar uniformity, the ,length of the oval being about one-eighth of an inch, and this about double and treble its width and depth respectively. Their surface was smooth and shining, their colour yellowish-white, and a viscid fluid in sparing quantity (probably synovia) united them into small clumps or masses. In consistence, they were softish, yet highly elastic, resuming their original size and shape immediately after the removal of a flattening pressure. A microscopic exami
nation showed them to consist of an uniform substance, and to be entirely- devoid of all traces of organization. Their chemical re action was that of an albuminous solid ; — viz. they were unchanged by water or ether, were shrunken by the application of alcohol, and were swelled out into a transparent mass by acetic acid. The substances described by Hyrtl differed in many important respects from the preceding granules. The synovial sheath of the flexor tendons was distended, so as to form a protuberance above and below the annular ligament of the wrist. Pressure on either of these swellings alternately gave rise to a predominance of the other one, and was attended by a kind of crepitating sound. On laying open the sheath, its interior was found to be occupied by upwards of a hundred small bodies, which in their colour and general appearance seem to have greatly resembled those described above ; but their consistence appears to have been softer, their size less uniform, varying from that of a hempseed to a lemon-pip, and their flattened shape was, in most instances, altered by the possession of an elongated extretnity, although others were more globular. The sac itself exhibited very interesting appearances. The tendons, where they passed through it, were greatly diminished in bulk. The parietal portion of the sac appeared to consist of two layers, a serous and a fibrous, the latter of which was dense. (Probably- this appearance was partly due to a condensation of the neighbouring areolar tissue by pressure into a membranous form, similar to that seen in the sac of an aneurism.) The synovial membrane, where it covered the tendons, was looser than natural, and had lost its smoothness and polish, while in many places it had acquired a villous appearance. In the subserous areolar tissue, little knots were seen, many of which projected into the sac, carrying before them a covering of the serous membrane ; others of them had rather a constricted neck; and, finally, in others this constriction had increased so as to form a peduncle of little more than the thickness of a hair. The severance of this connection brings these bodies to the same condition as the granules vvhich were found free in the cavity ; but the bulk of many of these was larger, while those yet in connection with the sac were uniformly of small size. This larger size of the un attached bodies was also noticed by Mor gagni. The minute anatomy of both the free and attached substances was the same. Their surface was clothed with an epithelium of angular flattened cells, and their interior contained areolar tissue and fat, with a grumous coagulated substance. These two normal tissues, however, were not in a healthy state; the fat cells were wrinkled, their con tents half solidified, almost opaque, and of a sordid yellow colour ; the areolar tissue was alike destitute of regular arrangement and of its ordinary wavy lines ; while with all this was mingled much aniorphous debris.