Experiments in Transplanting Lnnhs 273 



young developing nerve which has been deprived of its ganglion 

 is doomed to early disintegration. 



CONCLUSION 



The immediate result of the experiments in transplanting ex- 

 tremity buds to normal individuals is to show that, as far as the 

 acquisition of a normal peripheral nervous system is concerned, 

 it is quite immaterial whether the bud, prior to its transplanta- 

 tion, has developed in connection with the central nervous system 

 or not. It is likewise shown to be of no consequence, as regards 

 its nerve supply, whether a limb develops directly out of the trans- 

 planted bud or whether it arises later as an accessory or super- 

 regenerated appendage. These facts are in direct contradiction 

 to the premises upon which Braus bases his support of Hensen's 

 theory. The whole superstructure of his argument therefore 

 falls to the ground, and it will be necessary to build entirely anew 

 in inquiring into the bearing of the experiments upon the prob- 

 lems of the development of nerves. 



It is clear that the experiments do not hear directly enough 

 upon the point to decide satisfactorily questions of histogenesis, 

 though they do throw important light upon the manner in which 

 the peripheral distribution of the nerves is brought about. The 

 original experiment of Braus, confirmed in the present study, 

 shows that a normal limb bud, when transplanted to practically 

 any region of the body of a normal tadpole, will acquire a system 

 of peripheral nerves, which do not differ appreciably from the 

 normal in their arrangement, and which are connected with the 

 nerves of the region into which the limb is implanted, although in 

 normal individuals the latter nerves may have no relation what- 

 ever with the limbs. This fact, though in other respects of cardi- 

 nal importance, affords no solution of our problem because it may 

 be interpreted in accordance with either the primary continuity 

 or the outgrowth theories; either the nerves arise ni situ out of 

 structures present within the limb at the time of transplantation, 

 or they grow in from the nerves of the host and are guided to their 

 proper places of termination by the other structures within the 

 limb. 



