PART II.
TUMORS OF BONE.
Tur morbid growths comprised in the tumors of bone exhibit a great variety of characters. Some of them are peculiar to bone; others are analogous to the growths from soft parts. In some of them, moreover, the remark- able feature is seen, of the production of tissues identical with those which occur in the natural formation of bone. Thus, with respect to the cartilaginous, and to some of the osseous tumors, the cartilage, in the first, in no way differs from feetal cartilage ; and the osseous substance, in the second, presents all the features of healthy bone.
An arrangement of the tumors of bone cannot well be founded on the place of their origin, since many of them, identical in nature, arise indifferently from periosteum, the compact, or cancellous tissue of bone. Often, indeed, concurrently with the growth of a tumor from the outside ofa bone, a similar growth arises within it. Nor can an arrangement of these tumors be easily determined by their composition, two or more morbid products being occasion- ally united in the same tumor. Another source of diffi- culty in classifying the tumors of bone is the changes to which they are liable. Thus, some of these tumors, pro- bably from weakncss of their vital organization, when �
