CHAPTER XI 



SUGGESTIONS CONCERNING THE ORIGIN AND 

 DEVELOPMENT OF NEURON PATTERN 



ELECTRICAL POLARIZATION AS A LOCALIZING AND 



ORIENTING FACTOR 



Most of the special assumptions as well as most of 

 the difficulties involved in Kappers' hypothesis can, I 

 believe, be avoided by considering the reaction of the 

 neuroblast, not simply as a matter of electrical attrac- 

 tion, but rather as a change in physiological condition, 

 resulting primarily from the electrical polarization of 

 the cell through the action of the current to which it is 

 exposed. When an electric current passes through any 

 conducting medium in which ions are free to move, 

 negative ions (anions) migrate toward the positive pole 

 or anode and positive ions (cations) toward the negative 

 pole or cathode. From this migration of the ion? 

 electrical polarization results. If the current passes 

 through a living cell, it is evident that ions of opposite 

 sign must migrate in opposite directions in the cell, and 

 if the cell possesses a membrane which is not completely 

 permeable to ions, and cells in general do possess such 

 membranes, the ions of opposite sign must accumulate 

 to some extent at opposite poles of the cell inside the 

 membrane, the positive ions on the side toward the 

 cathode, the negative ions on the side toward the anode. 

 The cell is then electrically polarized and this polariza- 

 tion must determine changes in its physiological condition 



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