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 
betwten 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 i in the animal type of intel- 
lect and i in the adaption of his brain to it be at the bottom 
of \nig’§ 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. 
