42 H. V. NEAL 



for its support largely upon the well established fact of the cellular 

 structure of embryonic nerves. It was this fact that caused 

 Kupffer finally to abandon his process theory. Then also von 

 Apathy's important discoveries of the intercellular relations 

 of the neurofibrils have seemed to some to favor this view of 

 neurogenesis, so that the theory appears to have a new lease of 

 life. Bethe ('03) is of the opinion that he has established the 

 fact of the dependence of the axis cylinder upon the 'nerve cell' — 

 in the Apathy sense — because he finds that in his preparations 

 the mitotic division of a nucleus interrupts the nerve fiber. Held 

 ( '09) suggests that this evidence might warrant another inference 

 not complimentary to the quality of Bethe 's preparations. 

 Taken as a whole, the arguments in favor of this much discussed 

 hypothesis, which has derived the larger part of its support 

 from preparations unsuited to the requirements of neurological 

 investigation, seem most unconvincing. 



Held's ('09, p. 51) discovery of the polyneuroblastic origin 

 of nerve fibers should not be taken as a confirmation of the 

 cell-chain hypothesis, since it does not involve the idea of a 

 cell-chain but asserts the formation of some neuraxons by the 

 fusion of the processes of adjacent neuroblasts. 



Bardeen ('03, p. 255) and the writer ('03) have advanced 

 arguments against the claim that the cells of embryonic nerves 

 participate in the formation of the fibers of the nerves. In 

 this connection, Bardeen says that "in an early embryonic 

 nerve of moderate size one finds many hundred fibrils enclosed 

 by a sheath of flattened cells, but with no cells among them. 

 In such nerves one can most easily see that the fibrils are not 

 differentiated parts of cells lying in the nerve." 



The phenomena of motor nerve histogenesis in Squalus affords 

 no support to the cell-chain hypothesis, since somatic motor 

 nerves in this animal acquire connection with the myotomes and 

 a fibrillar structure before cells make their appearance within 

 the nerve .anlage. The cellular structure emphasized by the advo- 

 cates of the hypothesis appears only in somewhat advanced 

 stages in histogenesis. Evidence that the cell elements present 

 in the nerve anlagen have a genetic relation to the fibers or neu- 



