1. Transplantations of autografts and of Kiel bone to the iliac bone and to muscle tissue were performed in rabbits. Through labelling with two tetracycline compounds which have different fluorescent colours in ultraviolet light, bone formation between the labelling periods could be followed. 2. It was shown that bone formation between the fifth and the tenth day after transplantation to bone took place in about 50 per cent of the fresh autografts. Storage of the transplants in saline for one hour before replacement had little adverse effect, whereas exposure to air for one hour seemed to reduce the osteogenic effect of the grafts. Bone formation was not observed in grafts of Kiel bone during this period. 3. The fact that new bone formation in fresh autografts could be demonstrated even during the first four days after transplantation to bone indicates that osteogenic cells from the fresh autografts continue their activity under favourable conditions. This is supported by microradiographic and histological evidence. 4. The amount of callus which developed in close contact with the grafts during the first ten days after transplantation to bone was more pronounced both in fresh autografts and in autografts kept in saline than in autografts exposed to air for one hour. Callus developing at a later stage showed no significant difference between the various grafts, including those of Kiel bone. 5. In fresh autografts transplanted to muscle tissue callus formation could be demonstrated in most cases by the tenth day, indicating either survival of osteoblasts or the transformation of more primitive cells from the graft or from the host bone into osteogenic cells. No bone formation was observed when Kiel bone was embedded in muscle tissue.
1. The development of sclerosis of the femoral head after fracture of the femoral neck has been investigated by a combined microradiographic and histological examination of twenty femoral heads removed during arthroplasty of the hip done at varying intervals after fracture. 2. Mineralisation of the bone did not differ from the normal. 3. There was a direct correlation between the density of the femoral head as judged radiologically and the width of the trabeculae. In cases of sclerosis of the femoral head the trabeculae were broader than normal and histological examination showed that this was caused by apposition of new bone upon the necrotic trabeculae. 4. Although sclerosis is a result of necrosis, it is at the same time a definite sign that revascularisation and restitution are going on.
