46 DEVELOPMENT AND PURPOSE CHAP. 



of excitement permeating all available channels without 

 differentiation. In the higher organisms such channels are 

 clearly marked, and the excitement will always run .mainly 

 along nerve fibres and will affect the tissues innervated, 

 not only the muscles but of course the viscera. Indeed, 

 the imperative need felt for muscular action in cases of 

 powerful emotion probably arises from the necessity of 

 relieving heart, lungs, stomach and bowels from the strain 

 which otherwise falls exclusively on them and produces 

 intense discomfort and possibly serious ill effects. In the 

 lowest organisms the channels are less distinct, and excite- 

 ments sometimes propagate themselves through the whole 

 mass of protoplasm. If there were no channels at all 

 there would be a wholly undifferentiated discharge, yielding 

 a quite random reaction to any and every kind of stimulus. 

 Whether such complete absence of differentiation has ever 

 existed may be questioned. But we can recognise the 

 existence of discharges which are undifferentiated in the 

 sense that they permeate all available channels indifferently. 

 Such discharges occur in man mainly where purposive 

 action fails or where the excitement is too strong to be 

 readily contained, but if neither purpose nor any other 

 form of adaptive correlation existed they would be normal. 

 Undifferentiated discharges with the random actions to 

 which they give rise are what remain when all correlation 

 is taken away. Conversely, we may regard them as the 

 material out of which those forms of reaction are selected 

 which tend to secure the vital needs of the organism. 



B. CORRELATED ACTION. 

 I. CORRELATION BY HEREDITY. 



(i) Structural Activity. 



Uncorrelated action, it need hardly be said, is the 

 exception in animal life. In all living beings normal 

 behaviour runs on lines which roughly or accurately, in 

 broad sweep or in detailed precision, coincide with the 

 temporary or permanent requirements of the organism. 

 At the basis of this adjustment lie the modes of action 



