presents the peculiar characters of true cancer; and it frequently assumes that form of degeneration which has been variously termed Medullary Sarcoma, and Fungus Hasmatodes. Before any of these morbid conditions, however, are so fully developed as to be traced with accuracy, it commonly happens that the parts in the vicinity have put on the same action, and have become more or less connected or massed with the diseased periosteum.
It is proper, however, in a treatise of this kind, to state, that the periosteum is not exempted from those morbid changes which affect other tissues.
3. The periosteum, after having undergone those alterations in structure which are the result of chronic inflammation, sometimes remains permanently thickened, and acquires a cartilaginous hardness. When this is the case, the vessels of its tissue put on a new action, and the earthy matter of bone is deposited. This deposite, from its close approximation to the bone, in process of time becomes united with it, and gives rise to an affection resembling, in some of its external characters, true Exostosis. Ossified periosteum, however, is commonly of a denser texture than exostosis; and
