1. A quantitative method is described and a basic curve developed, indicating the breaking strength of regenerating bone.
2. Strength first manifests itself by the sixth day and then increases rapidly to the twenty-first day. It was observed that the callus grew steadily larger during this time.
3. There is a period of decline in strength after the twenty-first day, during and following which time the callus decreases in size.
4. There is a secondary rise in strength from the thirty-third to the forty-fifth day.
5. A strength is attained on the twenty-first day which is comparable to that on the thirty-ninth, but a period of weakness exists between the two.
6. There is a direct-correlation between the results of this study and previously observed histological facts and clinical data.