CHAPTER V 



THE PHYSIOLOGICAL GRADIENTS IN RELATION TO 

 ORGANISMIC INTEGRATION 



It is evident that a simple excitation- transmission 

 relation constitutes, at least momentarily, a physiological 

 integration, in which the point of primary excitation 

 becomes the dominant or controlling factor, since it 

 initiates the transmitted change and determines what 

 shall occur at the various points along the path of trans- 

 mission. Moreover, this relation is the physiological 

 basis of nervous function and integration, and this in turn 

 represents the highest degree of physiological integration 

 which has been attained in the course of evolution. It 

 was pointed out above (p. 17) that the excitation- 

 transmission relation is the most general and most 

 primitive relation of organismic as distinguished from 

 purely protoplasmic character, and I have endeavored to 

 show that the axial gradients originate as excitation gra- 

 dients. From this viewpoint the excitation-transmission 

 relation appears as the basis both of the beginnings and 

 of the most complex and highly developed features of 

 organismic integration, viz., nervous integration. Such 

 a conception has at least the advantage of placing the 

 problem of organismic pattern and integration before us 

 in definite and consistent physiological terms. 



The role of the physiological gradient as an integrat- 

 ing factor follows necessarily from the fact that it is a 

 gradient. Once established it brings different regions 



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