58 



Scientific Proceedings (51). 



of blood clot. The experiment was performed in the same way 

 as the previous one except that blood clot was placed in the peri- 

 osteal gutter left by the raised rib. After periods of 48, 44, 39, 23, 

 and even 14 days, the whole area was found to be occupied by a 

 calcareous material. Two ribs in the same animal were similarly 

 treated with the exception that in one no blood clot was used. 

 The one containing blood clot showed considerably more bone 

 formation. This showed the marked increase of bone in the 

 presence of blood clot. 



In order to rule out ingrowth of bone from the side, the follow- 

 ing method was resorted to. Extensive resections of a rib from 

 near the vertebral junction, to and including about 1 cm. of costal 

 cartilage. Hot paraffin was poured in at the vertebral and sternal 

 sides, allowing a free gap between. This gap was filled with blood 

 clot and all sutured in place. In four experiments of this nature 

 there always was found calcareous material, separated grossly 

 from any bony tissue. A few experiments without blood clot 

 were used as controls to the last. These showed some calcareous 

 material. In one particular instance considerable bleeding was 

 noticed at the end of operation, and in this case a heavy bony 

 deposit occurred. Thus the factor of post-operative hemorrhage 

 might explain discrepancies of results of these experiments and 

 those of other experimenters. 



An interesting point was noticed in cases where costal cartilage 

 was dissected away, in that there was an especially marked 

 tendency for regeneration of bone at costal cartilaginous junction. 

 If we consider this junction as an epiphysis it is remarkable that 

 we should get so much regeneration after its destruction, evidently 

 from the periosteum. 



In these experiments the periosteum has been considered as 

 one usually leaves it after surgical removal of bone. In conclusion 

 it appears that periosteum under certain conditions has the power 

 of regenerating bone, especially in the presence of blood clot. 

 Also, that it always exerts a stimulating effect on bone formation. 



