58 SUPER-ORGANIC EVOLUTION 



differentiation (vide fig. 9, p) ; the protoplasmic 

 prolongations have considerably increased through 

 their higher grade of evolution. 



The central prolongation (fig. 9, c) appears with 

 its ramifications. The peripheric prolongation 

 continues with its shoot and its ramifications. 



As we shall see by the diagrams, the com- 

 plexities follow each other in a methodical way. 

 By the side of this neurona we see neuroglic cells, 

 which have been perfectly studied in birds by Dr 

 D. Claudio Sala, who is such a great authority on 

 these subjects. 



Cerebral Cortex of Mammiferce (a rat a month 

 old). The trunk appears much more differentiated 

 here, and with a greater number of protoplasmic 

 expansions (fig. 10, d). The central prolongation, 

 with increasing ramifications (fig. 10, c). The 

 peripheric prolongation in one of the neuronas 

 (fig. 10, e) is seen with a large sprout whose small 

 tuft divides near the surface of the brain. By the 

 side we see some neuroglic cells and the edge 

 of a small artery. 



Human Cerebral Cortex (a child thirty days old). 

 Fig. 11 shows us at once the enormous change 

 this neurona has attained in man. The illustrious 

 Spanish neurologist Ham on y Cajal calls it the 



