NERVOUS SYSTEM 



53 



toward a more intelligent condition are found in their 

 heads. We may glance at this briefly. 



T'ni r — Pmy 



Fig. 24.— Skull of R<n)a escnientn. A, from above ; B, from below ; 

 C, from the left side, .r, parasphenoid ; y, girdle-bone ; Z, the 

 ' ' temporo-mastoid. ' ' 



The lowest animal tissue, where no nerves are ap- 

 parent, seems to be able to feel, or to draw back or go 

 on when touched. In this case it is supposed that 

 feeling goes through any part in any direction, from 

 one cell to another, where there is more than one 

 cell. But as in time there came to be special cells for 

 digesting, breathing, etc., so there came to be special 

 cells for feeling and for stimulating other cells into 

 action. These arranged themselves in rows, so they 

 could communicate with each other, and these rows 



