1 78 THE ORIGIN OF THE NERVOUS SYSTEM 



current is by no means certainly an excitation, as 

 Verworn regarded it. As a matter of fact, if the current 

 is long continued or sufficiently strong, death and dis- 

 integration begin in this anodic extension. Kappers' 

 assumption of increased permeability to anions in the 

 anodic extension also seems to involve difficulties. In 

 the current the anions migrate toward the anode, and 

 unless the concentration of electrolytes in the medium 

 surrounding the neuroblast is very much higher than 

 inside the cell, which cannot be the case, the anions 

 must migrate out of the cell toward the anode instead 

 of into it. Consequently the anodic extension ought, 

 according to Kappers' assumptions, to become more 

 electropositive internally and therefore to grow toward 

 the cathode, instead of becoming more electronegative 

 and growing toward the anode, as he maintains. While 

 these and other difficulties make it impossible to accept 

 Kappers' hypothesis as it stands, there can be no ques- 

 tion concerning the significance of the facts to which 

 he calls attention, and concerning the difficulties involved 

 in any attempt to interpret them in any other terms 

 than those of relations of some sort to electrical factors. 



