Abstract
1. An experimental study of the healing mechanism in circumscribed defects in femora of albino rats of the Wistar strain is described.
2. Only the outer one-fifth of the defect is repaired by subperiosteal bony callus, the rest of the defect being repaired by endosteal callus.
3. Subperiosteal callus does not bridge the defect until endosteal callus is developed fully.
4. As peripheral callus matures the greater part of the endosteal callus is resorbed, with the exception of trabeculae attached to the margin of the defect.
5. The resorbed area in the medullary part of the defect is gradually obliterated by deposition of inner circumferential lamellae.
6. There appear to be differences between the mechanism responsible for repair of fractures of a long bone and that which heals circumscribed bone defects.
