The joints are often affected by rheumatic and gouty inflammation; and there are three species of disease, tolerably distinct in their pathological characters, generally attributed to these causes. In one there is a deposit of chalky-looking matter, composed chiefly of super-lithate of soda, on the articular surfaces of the synovial membrane and cartilage, but most abundantly in the cellular tissue outside the joint, an affection in which the cartilage is seldom known to ulcerate. In the second, the cartilages are atrophied, as if worn away by attrition, the articular surfaces of the bone being much modified in shape, more or less denuded of cartilage, and remarkably polished and hard, so as to have been compared to porcelain, as will be described in another section. In the third, the fibrous tissue in the neighbourhood of a joint is primarily affected, the synovial membrane and cartilages not becoming involved till the disease is much advanced. It is not uncommon in the elbow of middle-aged persons who have been much exposed to the atmospherical vicissitudes, and is sometimes attributed to the effect of mercury or syphilis. The periosteum around the articular ends of the bones becomes swelled and painful; the affection is very slow in its progress; abundant deposition of adventitious bone takes place, often in short spiculæ, gradually encroaching around the joint, which ultimately becomes involved. A good specimen is here given. The disease was of twelve months’ duration, and was attributable to rheumatic inflammation supervening upon sprain. The affection involves extensively all the bones composing the articulation. Although wounds penetrating the larger joints are attended with danger, the synovial membranes are possessed of considerable powers of reparation, and often heal readily after severe injuries. An occasional result of inflammation is adhesion between the layers of the membrane, but this is by no means so frequent as in the serous tissues. The reparative power of cartilage is so low that the best termination that can be expected from the ordinary forms of ulceration, is union between the abraded surfaces. In experiments which have been made on the lower animals, portions of cartilage which had been removed from their joints were never reproduced, but the functions of the part were soon restored by the cut surface becoming smooth. In like manner there is occasionally to be seen in museums a circumscribed indentation in human articular cartilage, as if it had been destroyed by a small ulcer in this situation, which had cicatrized without any reproduction of the destroyed tissue. ON HYPERTROPHY AND ATROPHY OF THE ARTICULAR CARTILAGES, WITH EBURNATION OF THE SURFACES OF THE BONES.