Other conjectures as to the mode of their development are offered by Bidder, such as the possible precipitation of synovia around an epithelial cell, the gigantic development of a cell, or, what much approximates to this, their hydatid nature.
In certain abnormal conditions of the ar ticular cartilages, peculiar appearances of the synovial membranes are seen, although it is somewhat doubtful how far they can be re garded as essentially morbid.
Thus, for exarnple, in the ulceration of diar throdial cartilages, it appears probable, that the removal of their substance is chiefly accomplished by the sy novial membranes. Cruveilhier * narrates a case in which puru lent fungosities of this tissue replaced the destroyed cartilages of the ankle-joint; and the general connection of hypertrophy of the membrane with ulceration of the cartilage has long been known. More recently, Mr. U'ood sir's t investigations have thrown much ad ditional light on this subject. He has shown that the preternaturally active grovvth of the cartilage, and the similarly rapid change of its properties and appearances, are to be regarded as inherent in this tissue itself; that where the destruction of its substance occurs at its margin, or in the immediate neighbourhood of the vessels, a fungous enlargement or ex tension of these accurately fits into the eroded part ; but that in the ulceration of the centre of the cartilaginous lamella, such a physical adaptation is absent. From these circum
stances it seems probable that the absorption which is accomplished in the former case by the local enlargement, is in the latter shared by the vessels of the synovial membrane generally.
A somewhat similar, but much less pro minent affection of vascularity has been de scribed by Dr. Todd in the porcelain-like condition of these cartilages, which often obtains in the chronic gout of the aged. The highly injected vessels of the synovial membrane were covered by a whitish powder, which was doubtless a frictional detritus of the diseased cartilage. How far this con gestive state is connected with the absorption of this powder, is unknown.
(William