Experiments in Transplanting Limbs 245 



oWn experiments show, contrary to those of Braus, a normally 

 arranged nervous system does usually develop in the "aneuro- 

 genic" extremities. 



The third point which Braus makes is, that while the nerves 

 which connect transplanted limbs with the central nervous system 

 of the host are extremely minute, those within the limb are almost 

 as thick as the nerves in the normal limb. As Braus points out, there 

 are obviously two possible arrangements which may account for 

 this condition; either there are some fibers in the transplanted limb 

 that are not connected with nerve fibers of the host, or the fibers 

 connecting with the host branch frequently as they enter the 

 grafted appendage. Since it has not been possible to determine 

 by direct observation which of these alternatives is true, Braus 

 has attempted to settle the question indirectly. He is led to 

 reject the latter alternative and in accepting the former concludes 

 that the fibers in the grafted leg are developed autochthonously. 

 The first consideration which Braus adduces against the idea of 

 division is that the number of neuro-fibrils in the peripheral part 

 of the nerve is much greater than in the connecting strands, and 

 since according to Apathy the fibrils in peripheral nerve fibers 

 do not bifurcate, the peripheral increase cannot possibly be 

 accounted for in this way. This, to say the least, is an extremely 

 hazardous conclusion to draw, for it has never been shown with 

 any degree of certainty that the fibrils do not divide in the axones 

 of vertebrates. In fact there is now considerable positive evi- 

 dence that branching does take place. Dogiel has show^n this to 

 be the case in the nerves running to the corpuscles of Herbst and 

 Grandry, and Ramon y Cajal in certain cortical axones. Retzius 

 has demonstratejl that the fibrilkT increase in number on either 

 side of the nodes of Ranvier and quite recently SchiefFerdecker 

 has confirmed and extended this observation, showing that in 

 peripheral nerves of the frog finer fibrils coalesce at the nodes ot 

 Ranvier into a small number of much coarser threads, which, 

 after the node is passed again break up into the finer fibrillae. In 

 other words the neurofibrils of a peripheral nerve form a network. ^^ 



'^Schiefferdecker ('06a) discusses at length the relations and mode of branching of the fibrillas both in 

 the cell body and in the axis cylinder. 



