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 
