VEETEBKATB SYSTEMS 435 



lower vertebrates , the increase in size has been met by 

 doubling and folding one part upon the other, while in the 

 higher forms the wrinkling or furrowing of the cortex 

 gives increased surface. 



Along with these physical changes has come increased 

 mental power, until, in man, we have an animal preeminent 

 over all others by virtue of the superior mental powers. 



