PHYLOGENY AND ONTOGENY OF NEURON A 53 



is independent of the complexity of the animal. 

 In the olfactory sense of man these neuronas have 

 the same form. 



We must keep this bipolar form well before us, 

 because, as from the ectodermic cell one arrives 

 easily at the bipolar neurona, by fixing the at- 

 tention well on this form it is easy to understand 

 the changes which it goes through until we arrive 

 at the neuronas in the brain of man. 



Cerebral Cortex of the Batrachi. These animals 

 are the first in which the cerebral cortex appears 

 differentiated, which is the point to be dwelt upon, 

 so that the evolution of these centres should be 

 understood. 



In spite of the jump we have taken in organisa- 

 tion, it is easy to recognise at first sight the same 

 bipolar nerves of which we have spoken as a 

 typical form. The body remains equal (p); its 

 central prolongation is the same. The peripheric 

 prolongation, however, appears complicated with a 

 series of thorns throughout its branches. They 

 have somewhat the appearance of seaweed ; this 

 disposition of the cerebral cells is retained by 

 the peripheric branch till it reaches the neurona 

 of man. 



In the same diagram is a cell of the same 

 epithelial origin as the neurona, and its object 



