A mere lack of use of bones may also lead to a certain amount of atrophy from lacunar resorption. This may be seen after amputations, where the stump of bone which is left from the amputation slowly undergoes lacunar resorption and sometimes a marked diminution in size. The same thing may also be seen in the bones of people who for long periods of time have been deprived of the use of their limbs, either by the application of apparatus around fractures, or by disuse for other reasons. Lacunar resorption also occasionally follows lesions of the central nervous system, part of the atrophy being due to disuse of the limbs from the paralysis, and part of it also being dependent in some indirect way upon the nerve lesion. Atrophy of bone also may be brought about by pressure. It is to be remembered that the bone, as a matter of fact, is not a perfectly rigid material, but that processes of new formation and resorption are constantly taking place, even under normal conditions. If, for any reason, bone is put under constant pressure, a certain amount of readjustment of the bony constituents takes place in order to adapt the bone to its altered condition. The most striking example of this sort of atrophy is perhaps the Chinese ladies’ feet, where the bones, being bent into an abnormal position, beginning early in childhood, ultimately show enormous deformity and an entire rearrangement of the trabeculae of the bone. The same thing also may be seen occasionally after pressure and deformity from contracture of muscles or from the pressure of scars. This process, which ordinarily leads to loss of function, in a certain limited number of cases aids function, for whilst certain fractures of the joints may lend to deformity of the articular facets of those joints, by absorption of certain portions and new formation in others, a readjustment of the joint surface may take place, so that a marked increase of function may occur. A certain amount of atrophy also may be brought about by the pressure and development of tumors. +Hypertrophy of Bone.+ In many cases new growth of bony tissue is due to the new formation of periosteal bone, and is an expression of an attempt at repair of one or the other of the numerous destructive processes. In other cases true hypertrophy of the bone, with no connection with any reparative process, may occur. A notable example of this is seen in the growth of bone which sometimes occurs after amputation, especially in young people. The increased size of the bones which is seen in many definite diseases will be mentioned under the proper headings. +Caries and Necrosis.+ Various pathologic processes produce destruction of bone. The destructive process may cause the death of large areas of the affected bone at once, and in that case, a large fragment of necrotic bone may remain in situ and still maintain its contour. Destruction of bone of this sort is described by the clinical term _necrosis_.