Mental Evolution. 491 



in harmony with the other neural processes of the cerebral 

 hemispheres. The brain is a microcosm; its neural pro- 

 cesses are interrelated ; and the environment of any neural 

 process is constituted by other neural processes. 



A little consideration will show that this must be so ; 

 that it is only the physical or kinetic aspect of what is 

 freely admitted when the mental or metakinetic aspect is 

 under consideration. If it be admitted that states of con- 

 sciousness are determined by other states of consciousness, 

 and that states of consciousness are the concomitants of 

 certain neural processes in the brain, it follows as a logical 

 necessity that brain-neuroses, however originating, are 

 determined in their evolution by other brain-neuroses ; and 

 that there has been a brain or interneural evolution, 

 distinct from and yet intimately associated with the 

 evolution of other bodily structures and activities. The 

 more closely and directly brain-neuroses are associated 

 with immediate activities, the more closely implicated is 

 interneural evolution in the process of organic elimination 

 through natural selection. But when long trains of neuroses 

 take place in only remote and distant connection with 

 other bodily activities, they are removed from the process 

 of elimination through natural selection, and interneural 

 evolution is allowed to proceed comparatively untrammelled. 



I have already indicated my belief that abstraction 

 (isolation), analysis, and conceptual ideas have been 

 rendered possible through language, and are excellences 

 unto which the lower animals do not attain. Hence I 

 regard this comparatively untrammelled phase of inter- 

 neural evolution as something essentially human, something 

 which differentiates man from brute. And I would correlate 

 man's greatly developed brain — inexplicable, I think, by 

 natural selection alone — with this later and special phase 

 of interneural evolution. Even in the lowest savage this 

 brain-evolution has proceeded a long way. I am not fitted 

 in this matter to offer an opinion which would carry much 

 weight. But from all that I have read I gather that 

 savages have in all cases elaborated a complex — often a 



