THE REFLEX ARC 265 



development of the cortex must be in large part electri- 

 cal in origin. The anatomical and functional relations 

 of the cortex paths indicate clearly enough that condi- 

 tions there are unique as regards complexity, though not 

 different in kind from those in other parts, and it is dim- 

 cult to conceive any other than electrical factors which 

 could determine these relations. If we could trace out 

 the electrical gradients and their changes and the 

 sequence in which different body regions and organ 

 primordia affect the cortex region electrically, either 

 through developmental activity or functional excitation 

 and so bring about physiological changes in this region, 

 we might attain some conception of the basis for its 

 remarkable structure and function. 



The evolutionary aspect of the origin and develop- 

 ment of the upward paths and of the cortex is of course 

 another matter, involving, as I have repeatedly pointed 

 out, the hereditary mechanism of the protoplasm con- 

 cerned. In other words, the gradient situation works 

 out differently in different protoplasms, and in those in 

 which it works out in certain ways a cerebral cortex and 

 the other features associated with it appear. Whether 

 the evolutionary process requires Lamarckian assump- 

 tions or not does not primarily concern us here, but the 

 gradient conception does not make such .assumptions 

 necessary. However the necessary mechanism of proto- 

 plasm is established, the development of the individual 

 is a physiological process, and real advance in our con- 

 ceptions of heredity is possible only as our knowledge of 

 the physiology of development increases. The con- 

 ception of the physiological gradient and of its relation 

 to development and integration places these problems 



