Sarcoma And Cysto-Sarcoma occur in bone pretty frequently; they are sometimes situated on its surface, and sometimes developed in its interior. When deeply seated, they usurp the place of the natural bone, and produce atrophy of it by their pressure; or else distend it so that it forms a more or less complete shell. Just as, usually, the tissue of the bone in the neighborhood of the growth acquires increased density (sclerosis), so, when the morbid growth is superficially seated, a development of new bone takes place, which projects into it in processes like thorns and leaves. And when the morbid growth is of the sarcomatous kind, it is not only encased in an osseous shell, but the bone adjoining the shell enlarges sometimes very considerably, and especially in thickness, while knotted cords of new bone are developed in the tumor, and traverse it in different directions.