CARTILAGE. 



497 



animal sensibility is exceedingly low, scarcely 

 perceptible, yet it probably does exist, and 

 will manifest itself whenever any cause is 

 operating upon them which might destroy their 

 texture. We may, indeed, cut an exposed car- 

 tilage without pain, and the violent pressure it 

 undergoes in a sound joint is unheeded. But 

 the former is a kind of injury from which car- 

 tilage may be said to be totally exempted, and 

 the latter is that for which it is peculiarly 

 adapted. In either case sensibility would be 

 useless or inconvenient. Let but a foreign body 

 however get into a joint, between its cartilages, 

 such as might disorganize them, and then an 

 alarm is set up too great to be attributed to the 

 synovial membrane alone, and depending, we 

 may suppose, in part at least, on the cartilage 

 itself. 



C. ACCIDENTAL CARTILAGE. By this name 

 we designate the cartilaginous concretions which 

 are occasionally found in situations where they 

 do not ordinarily exist. They present them- 

 selves in several organs, under various forms, 

 and in different stages of development. Laennec 

 divides them into perfect and imperfect ;* but 

 it is not easy to point out any line of distinction 

 between these two classes; they differ only in 

 degree, the one passing gradually into the other 

 as its development becomes more complete. 

 We rarely, indeed, meet with accidental car- 

 tilage which deserves to be called perfect ; in 

 one part it is fibrous, or of a dense cellular 

 nature, in another it is cartilaginous, while a 

 third portion of the same piece is passing into 

 the osseous state. 



The forms and situations in which they 

 occur, will permit an arrangement of them 

 under three heads : 



1. The insulated or loose cartilages, which are 

 found either (a) in joints or (6) in serous sacs. 



a. Those of the joints are rounded or ovoid, 

 usually flattened, sometimes lobulated, always 

 smooth, polished, and lubricated with synovia, 

 frequently osseous in their centre. They vary 

 in magnitude from the size of a mustard-seed 

 to that of an almond ; and in one instance Mr. 

 S. Cooper found in the knee a concretion of 

 this kind, which was as large as the patella. 

 They also vary considerably in numbers ; Haller 

 saw twenty in the articulations of the lower 

 jaw, and Morgagni met with twenty-five in a 

 knee-joint. Their most usual seat is in the 

 knee, but they have been found in the hip, 

 jaw, elbow, and wrist. They are commonly 

 " loose," moving freely in the cavity, but some- 

 times connected to the synovial sac by slender 

 membranous attachments. 



With respect to the origin of these bodies 

 various opinions have been entertained. Haller 

 and Reimarus supposed that they were frag- 

 ments of the original cartilage, accidentally de- 

 tached. Cruveilhier found fifteen of them in a 

 hip-joint some years after it had been injured, 

 and conceived that he saw an exact correspon- 

 dence between them and certain depressions in 

 the cartilages of that articulation. Bichat con- 

 jectured they might be altered portions of the 



* Diet, des Sciences Med. 



synovial membrane. According to John Hunter, 

 they may have had their origin in a coagulum 

 of blood poured into the joint from an injured 

 vessel, and there becoming organized. This 

 coagulum would, he thought, assume, as in all 

 other situations, the peculiar organization of the 

 parts in its immediate vicinity. Laennec and 

 Beclard were of opinion that they might be 

 formed outside the synovial membrane, and 

 push it before them so as to form a pedicle, 

 which in some cases remained, but more gene- 

 rally was ruptured. This opinion Laennec sup- 

 ported by observations made on similar sub- 

 stances in serous sacs, where he traced them 

 through all the degrees of their development, 

 from the incipient stage, in which they formed 

 a slight projection behind the membrane, to the 

 period when they became perfectly isolated 

 bodies. Sir Benjamin Brodie, whose authority 

 on this subject is of so much weight, remarks, 

 " It is generally supposed that these loose 

 bodies have their origin in coagulated lymph 

 which has been effused from inflammation of 

 the inner surface of the synovial membrane, 

 and which has afterwards become vascular. In 

 the majority of cases, however, which I have 

 met with, no symptoms of inflammation pre- 

 ceded their formation ; and hence it is probable 

 that, in some instances, they are generated like 

 other tumours, in consequence of some morbid 

 action of a different nature. They appear to be 

 situated originally either on the external sur- 

 face, or in the substance, of the synovial mem- 

 brane ; since, before they have become de- 

 tached, a thin layer of this latter may be traced 

 to be reflected over them."* 



When inflammation is of long standing in a 

 bursa mucosa, it is not unusual to find in it a 

 number of loose bodies, of a flattened oval 

 form, and of a light brown colour, with smooth 

 surfaces, resembling small melon-seeds in ap- 

 pearance. There seems to be no doubt that 

 these bodies have had their origin in the coagu- 

 lated lymph effused in the early stage of the 

 disease.f From the resemblance which these 

 concretions bear to loose cartilages, we might 

 infer that they both have had a similar origin ; 

 but, as there can be no doubt that loose car- 

 tilages sometimes begin to be formed outside 

 the synovial membrane, we must not conclude 

 that this is the only mode. 



From the evidence before us, therefore, and 

 from observations made on the second species 

 of accidental cartilage, to be mentioned by-and- 

 bye, we are inclined to admit two distinct 

 sources from which these loose cartilages may 

 have commenced. One, a deposit in the cel- 

 lular tissue outside the synovial membrane; the 

 other a deposit within this membrane. The ori- 

 gin of both being lymph, which becomes cartila- 

 ginous, and often proceeds to an osseous state. 



b. Insulated cartilages are sometimes found 

 in connexion with true serous cavities. They 

 are seldom larger than a pea, rounded, floating, 

 or attached by a pedicle to the inside of the 



* Pathological and Surgical Diseases of the 

 Joints. Lond. 1834. 

 t Idem. 



2 K 



