CHAPTER VI 



LOCALIZATION AND DIFFERENTIATION OF NERVOUS 



STRUCTURE IN RELATION TO THE 



ORGANISMIC PATTERN 



THE NERVOUS SYSTEM AS A PRODUCT OF 

 PHYSIOLOGICAL FACTORS 



According to the conception of organismic integra- 

 tion advanced in the preceding chapters such integration 

 is, at least in axiate forms, primarily excitatory and 

 transmissive in character, and the role played by chemi- 

 cal or transportative factors, hormones, etc., is secon- 

 dary, though of great importance, particularly in the 

 more complex, highly differentiated forms. 



If the organism were primarily nothing but an 

 aggregation of different chemical substances with the 

 possibility of chemical or transportative relations be- 

 tween them, it is difficult to understand how it could 

 ever become anything else; in other words, how a 

 nervous system with its excitation-transmission relations 

 could arise in it. But living protoplasm is something 

 more than such an aggregation of chemical substances, 

 because it is irritable, that is, it possesses the capacity 

 for excitation and transmission and therefore, as I have 

 pointed out, the possibilities of excitation-transmission 

 relations between different parts exist in it. Most 

 biologists are agreed that the appearance of a nervous 

 system in protoplasm docs not involve the origin of a 

 new functional activity different from the fundamental 

 activities of protoplasm in general. The current view 



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