THE PROBLEM OF NEURON PATTERN 173 



mental data concerning the neuron itself and in spite of 

 the difficulties, it seems worth while to point out certain 

 of the possibilites along this line of interpretation. 1 

 First, however, it is necessary to examine a hypothesis, 

 recently advanced by Kappers, of neuron polarity and 

 growth orientation in terms of response to electrical 

 factors. 



KAPPERS' THEORY OF THE ORIGIN OF NEURON PATTERN 



In a series of papers Kappers 2 has described certain 

 phylogenetic and ontogenetic processes of shifting or 

 migration of neurons in the nervous system, which he 

 has called "neurobio taxis." Neurobiotaxis consists, 

 according to Kappers (1917) in the following phenomena : 

 "The growth of the chief dendrite and eventually the 

 displacement of the cell-body itself takes place in the 

 direction whence the majority of stimuli proceed to 

 the cell. Only between correlated centers does this out- 

 growth or shifting take place." In the growth of the 

 axon also synchronic or successive stimulation plays a 

 part. In attempting to account for the apparently 

 directed outgrowth of dendrites and shifting of the cell 

 body as well as for the localization and directed outgrowth 

 of the axon Kappers has advanced the hypothesis that 

 the electrical field in which a neuron develops is the fac- 

 tor which determines its morphological polarity as regards 

 axon and dendrite. He interprets the growth response 

 of the neuron in the electrical field as a galvanotaxis, 

 the axon originating on the side of the neuroblast toward 

 the positive pole or anode of the field and growing 



1 See footnote on p. 205 below. 



2 See Kappers, 1917, and references there given; also Bok, 1915. 



