THE PROBLEM OF NEURON PATTERN 157 



The problem of the nature and origin of neuron 

 polarity has received comparatively little attention from 

 neurologists, and in view of the fact that experimental 

 data are lacking, any consideration of the problem at 

 this time will doubtless appear to some as a completely 

 futile undertaking. Neuron polarity and pattern are, 

 however, essential features of nervous pattern, and it is 

 scarcely possible in a discussion of the origin of nervous 

 pattern to ignore the problem of neuron pattern. In 

 its most highly developed form this pattern represents 

 a specialized type of intracellular axiate pattern which 

 appears in a very definite and orderly manner, though 

 with extreme variation and complication as regards 

 axial direction and spatial relations. We must at least 

 attempt to discover whether there is any basis for 

 believing that this pattern is similar in nature and 

 origin to other types of axiate pattern. Any exhaustive 

 consideration is of course impossible, but it is desired 

 to call attention to certain facts which appear significant 

 and to suggest certain interpretations which may possibly 

 point the way to an experimental attack on the problem. 



THE GENERAL MORPHOLOGICAL CHARACTERISTICS OF 



NEURON PATTERN 



Our knowledge of the morphology of the neuron is 

 based upon the extensive investigation of Golgi, Ramon 

 y Cajal, Ehrlich, Retzius, Bethe, and many others, and 

 an extensive literature has grown up, from which is 

 evident notonly the bewildering variety of neuron pattern 

 as regards detail but also certain general characteristic 

 features. As reference to any of the general works on the 

 histology of the nervous system will show, the following 



