No. 493] EXPERIMENTS LX GRAFTING 



3 



reverse direction in the pocket of skin of the same limb 

 shows that as a rule proliferation takes place from the 

 cut ends of the bones, both of the graft and of the stump 

 of the limb. In the majority of cases it is impossible to 

 decide with certainty whether the bones of the new limb 

 originate from one or from both sources. While such 

 a combined formation would be of interest in itself the 

 conditions are such as to make it impossible to assert that 

 both proliferations do actually contribute; for, even if 

 the new material from both sources is continuous with the 

 new material of the regenerating part, we can not be 

 entirely certain that both really take part, however prob- 

 able this may seem. In a few cases, however, where 

 the skeletal material of the new limb had connected with 

 the proliferating periosteum of the grafted piece there 

 was every indication that the new part was derived from 

 the exposed proximal end. In all cases that have formed 

 a new limb, the periosteum of the cut end of the leg- 

 bones has formed a bar of cartilage connecting their ends 

 with the nearest ends (the original distal ends) of the 

 bones of the grafted piece. Two possible errors make 

 other cases of doubtful value. The short pieces of 

 grafted bones are often turned obliquely, or even side- 

 wise in the end of the limb, due to the contraction of 

 the skin as the end heals, or to changes that take place 

 in the surrounding tissues.. In most other cases, the 

 periosteal tissue growing down from the cut end of the 

 leg-bones passes around to one side of the grafted piece, 

 and, with or without receiving contributions from the 

 latter, forms the cartilage of the new limb. In fact, in 

 some cases this can clearly be seen to have taken place, 

 in others, while not so evident, the possibility of such a 

 process exists and renders the result uncertain. 



