540 



SEROUS AND SYNOVIAL MEMBRANES. 



nation will apply to these unattached bodies 

 universally : it seems more probable that 

 amongst these substances are included some 

 which have not only a different origin, but 

 also a different relation to the synovial mem- 

 branes. 



Thus, it was imagined by Hunter* that 

 " the loose cartilages usually found in the 

 knee-joint originated from a deposit of coagu- 

 lated blood upon the end of one of the bones, 

 which had acquired the nature of cartilage, 

 and had afterwards been separated." He 

 conjectured that their pednnctilated shape 

 during the period of their attachment de- 

 pended on the movements to which such 

 deposits were liable during their soft con- 

 dition ; and in confirmation of this he adduces 

 an instance in which some blood effused in 

 the abdominal cavity acquired a peduncle 

 half an inch in length before it lost its red 

 colour, and, when washed, exactly resembled 

 a pendulous tumor. And as to the possibility 

 of the transformation of such an effusion into 

 a cartilaginous-looking substance, reference 

 is made to " an examination of joints which 

 had been violently strained or otherwise 

 injured, where the patients had died at diffe- 

 rent periods after the accident. In some of 

 these there were small projecting parts, pre- 

 ter naturally formed, as hard as cartilage, and so 

 situated as to be readily knocked off by any 

 sudden or violent motion of the joint." The 

 frequent connection of this variety of loose 

 cartilage with external violence has long 

 been known, and in some of these cases 

 symptoms of local inflammation mark the 

 period of their formation ; while, after a cer- 

 tain interval, the accident of their separation 

 occurs, attended by the ordinary effects on 

 the movements of the joint. 



These facts, however, while they afford a 

 great probability that external violence may 

 operate as a cause of these growths, by giving 

 rise to an effusion, which in some instances 

 consists, it is most likely, of blood ; yet they 

 do not exhibit the relation of this effusion to 

 the synovial membrane. But it may be con- 

 jectured from the situation and arrangement 

 of the vessels, that a sudden hemorrhage, to 

 any perceptible amount, would necessarily 

 imply the rupture of this delicate tissue, and 

 the consequent presence of the effusion in its 

 cavity ; while a smaller or slower process 

 would carry the membrane before it ; or, in 

 other words, that the presence or absence of 

 the serous covering would chiefly depend on 

 mechanical conditions ; and that, in either 

 case, the result would be little affected. 



Indeed, the synovial membrane itself cannot 

 be considered immediately essential to the 

 formation of these substances ; another vas- 

 cular surface may be substituted, the result 

 continuing the same. Thus, Sir Everard 

 Homef mentions a case in which thirty or 

 forty such substances were found loose in the 

 cavity of a false joint, having apparently been 



* Transactions of a Society for the Improvement 

 of Medical and Surgical Knowledge, vol. i. p. 231. 

 f Loc. cit. 



mechanically broken off from a number of 

 projecting portions of cartilage, which studded 

 the broken ends of the bones, leaving exposed 

 interstices. Although slight variations in the 

 size and shape of these substances, and more 

 considerable differences of their consistence, 

 are spoken of, yet their description essentially 

 coincides with that of the preceding bodies 

 examined by Bidder. 



Taken altogether, these facts seem to in- 

 dicate that the unattached substances which 

 are found in these tissues include the products 

 of very different pathological conditions and 

 processes. They appear to show that morbid 

 deposits beneath the synovial membrane, effu- 

 sions the result of violence, and either oc- 

 curring beneath it, or by mechanical extension 

 in its cavity, and finally, irregularly formed 

 cartilage, may all, under certain circum- 

 stances, give rise to the production of these 

 substances.* 



The conditions essential to their transform- 

 ation seem to be of a twofold nature, me- 

 chanical and physiological ; exposure to pres- 

 sure and movement, and the presence of a 

 synovial fluid. It is doubtful how far the ac- 

 quisition of the peduncle noticed in some, 

 ma}' depend on the joint influence of their 

 extensibility, and the mechanical violence 

 which must be exerted on such isolated pro- 

 minences. But the separation, whether of 

 these, or of those seen in the false joint, is 

 obviously the direct result of violence. Pres- 

 sure seems an important condition, so much 

 so, that a close relation may probably be 

 traced between its amount and the degree in 

 which they have assumed the cartilaginous 

 form and consistence ; the synovial sheath, 

 the knee-joint, and the false joint appear to 

 present gradations in both these respects. 

 And as to the operation of the synovial fluid, 

 similar probabilities may be deduced. The 

 mere permanence of these bodies seems to 

 point out that they possess some kind of nu- 

 trition; and the increased bulk noticed by 

 Hyrtl in the unattached as compared with the 

 attached substances, would still further ne- 

 cessitate such a supposition ; their structure 

 sufficiently denying the suggestion that the 

 increase is due to the union of two or more. 

 And in the case described by Hyrtl, the struc- 

 ture of these bodies seems to show that the 

 results of a previous organization are not 

 exempt from this transforming process, but 

 may. undergo a degeneration into a cartilagi- 

 nous substance. And in the absence of any 

 inherent or chemical capacity of their contents 

 for such a change, this would yet more re- 

 quire the supposition of an agent of nutrition, 

 which should supply the materials, if it did 



* I may, perhaps, mention, that since writing the 

 above, I believe myself to have verified the con- 

 version of bone into these structures. The change 

 was partial, and the vessels seem the immediate 

 agents of the process, since not only did a superficial 

 stratum of cartilage occupy the whole surface of a 

 pedunculated and cartilaginous structure, but a 

 layer of nearly equal thickness surrounded the 

 vessel in each Haversian canal. See Medical Ga- 

 zette of Dec. 8. 1848. 



