The Evolution of Human Intellect 287 



progress is a real fact ; it does exist as a possible vera causa; 

 it is thus at all events better than some imaginary cause 

 of the origin of human intellect, the very existence of 

 which is in doubt. In a similar manner we know that the 

 neurones, which compose the brain and the connections 

 between which are the physiological parallels of the habits 

 that animals form, show, as we pass down through the 

 vertebrate series, an evolution along lines of increased deli- 

 cacy and complexity. That an animal associates a certain 

 act with a certain felt situation means that he forms or 

 strengthens connections between certain cells. The in- 

 crease in number, delicacy and complexity of cell structures 

 is thus the basis for an increase in the number, delicacy 

 and complexity of associations. Now the evolution noted 

 in cell structures affects man as well as the other vertebrates. 

 He stands at the head of the scale in that respect as well. 

 May not this obvious supremacy in the animal type of intel- 

 lect and in the adaption of his brain to it be at the bottom 

 of his supremacy in being the sole possessor of reasoning ? 

 This question becomes more pressing if we realize that 

 we must have some sort of brain correlate for ideational 

 life and reasoning. Some sort of difference in processes in 

 the brain must be at the basis of the mental differences be- 

 tween man and the lower animals, we should all admit. And 

 it would seem wise to look for that difference amongst differ- 

 ences which really do or at least may exist. Now the most 

 likely brain difference between man and the lower animals for 

 our purpose, to my mind indeed the only likely one, is just this 

 difference in the fineness of organization of the cell struc- 

 tures. If we could show with any degree of probability 

 how it might account for the presence of ideas and of reason- 

 ing, we should at least have the satisfaction of dealing with 

 a cause actually known to exist. 



