Abstract
1. The utilisation of radioactive sulphur in vivo has been demonstrated both macroscopically and microscopically during the preosseous stage of bone repair.
2. The labelled mucopolysaccharide complex, chondroitin sulphuric acid, has been studied during the formation of the medullary and periosteal blastemata in the healing of a fracture.
3. The appearance and possible significance of mast cells adjacent to a fracture, and resulting from the stimulus of trauma, are discussed.
4. Cortisone has been seen to affect the formation of the periosteal cartilaginous blastema and subsequent process of endochondral ossification, with liberation of increased amounts of chondroitin sulphuric acid which was calcified rather than ossified.