One hundred and fifty-seven bone and callus transplantations to ulnar defects or to the gluteal muscles of rabbits were performed. The specimens were studied by routine histological methods, as well as by stains for collagen, alkaline phosphatase, and phosphates.

Although homogenous bone was usually well incorporated, best results were obtained with autogenous iliac bone. Shave grafts of tibial bone incited extensive osteoclastic and fibroplastic reactions, and were almost completely destroyed before healing of the defect occurred. The mechanism of destruction of the grafts has been discussed in the light of preliminary in vitro experiments involving bone digestion. Alkaline phosphatase localization and its role in osteogenesis have been briefly discussed.

Although peripheral areas of trabeculated iliac bone and of callus transplanted to muscle tissue occasionally survived, all such transplants to bone defects became necrotic, indicating that the speed of revascularization of a graft bed is probably the principal determining factor in maintaining viability of transplanted elements.

There was no evidence of direct osteogenetic stimulation by any elements of the transplanted fragments.