It has been said that the bone cell is the most physically stable and the most biologically labile of all the cells in the animal body. This is substantially true: while the bone cell gives permanent form and rigidity, there is no cell in the body that is more subject to the influences of variations in diet, to the effect of chemicals and to pathologic processes.
A conspicuous concomitant of bone disease is bone production. Bone production may occur simultaneously and alongside of bone, showing recessive changes. Production of new bone is a response to bone invasion from many causes. It is strikingly absent in a large group of diseases of bone, among which should be mentioned the cystic degenerative processes and the so-called deficiency diseases, myeloma, metastatic bone tumor and a large group of primary osteolytic sarcomas.
In those processes in which new bone occurs, the manner and form