Abstract
The absorption of bone in Gruneberg microphthalmic mice and the op op osteopetrotic rat can be stimulated by an injection of compatible bone marrow; complete resorption can occur. The bone-absorbing osteoclast responsible probably is derived from a hematopoietic stem cell resident in the bone marrow. Maintenance of the resorption depends on the survival of donor cells which has an important implication for clinical therapy in man. No evidence was found that the thymus played a leading role in the mechanism of bone absorption in the Gruneberg microphthalmic mouse or in the op op rat. [The osteoclast is a specialized phagocyte.].