The interarticular adipose tissue also seems to be increased in volume, from being infiltrated with a serous fluid, by the discharge of which the diseased bloodvessels may have attempted to relieve themselves. When the inflammation has been intense, or of long duration, lymph is secreted, and deposited on the external surface of the membrane, forming an intimate union between it and the ligaments, and producing thickening of the external apparatus. Or the lymph is also effused on the inner surface of the membrane, to which it adheres and becomes organised; this is generally accompanied by the formation of purulent matter; the organised effusion is often so extensive as to conceal almost the whole of the synovial membrane, excepting portions of its delicate reflexions which invest the articulating cartilages. By the lymphatic deposit, to a less degree, the folds also of the synovial membrane adhere to each other, whereby the motion is still farther impeded, and the pain, when attempted, increased. Occasionally the synovial membrane is found enormously thickened, much softened in texture, and of a brown hue, when the disease has been of a very chronic character. Along with these appearances, serum is generally found effused, in a greater or less quantity, into the cellular tissue exterior to the ligamentous covering. In cases in which the matter has formed and remained long within the cavity of the articulation, the synovial membrane and the ligaments become blended into one soft mass, the internal surface of which is lined with a thick coating of lymph, as in the case of common abscess. If purulent matter is effused externally, and communicate with the joint, the capsular ligament will be found to have ulcerated and given way at certain points, forming apertures, usually of small size, and with ragged margins. [Illustration] All these appearances may exist without disease of the cartilages or extremities of the bones; but generally they are also affected at the same time. At first the surface of the cartilage is slightly irregular and rough, and the change is not observed, unless on minute inspection. Afterwards the surface is marked with small depressions, which may be numerous, and are surrounded with irregular and somewhat serrated margins. They gradually increase in depth and extent, and the subjacent bone is ultimately exposed at one or more points, as here shown. Often the greater part of the cartilage is removed by absorption; the bone is exposed, opened out in its texture, softened, of an irregular surface, and in some places excavated, containing a thin ichorous fluid; the process of ulceration has also extended to the osseous tissue. Sometimes scales of cartilage of considerable size are either completely detached, having become dead, and been thrown off by the natural process, and are found lying loose in the cavity of the articulation; or they are all but separated, adhering by one or more very slender attachments.