43^ ^Journal of Cojnparative Neurology and Psychology. 



which has hitherto been unknown, and that particularly it is a 

 source of much stimulation and clarification in the realm of sense 

 psychology. You will recognize with me that even today the 

 constitution of the brain in the lower vertebrates enables us to 

 predict most of the activities which we observe in these animals. 

 I divide the brain into the palceencephalon and the neencephalon. 

 The palaeencephalon appears, with all its characteristic sub- 

 divisions, from cyclostomes to man. No part is ever entirely 

 absent; its type remains unchanged whether we have before us 

 the brain of a shark or the brain of an elephant. It is the oldest 

 portion of the entire central nervous system, and many animals 

 possess nothing but it. The neencephalon, however, develops 



(,irj^;&u^j^ 



Lob acust lal 



lob vagi 



Crimes lat. /Jypop/i. "'^^^ 

 Fig. I. Brain of Chimaera monstrosa. 



above fishes. From very small beginnings in the selachians it 

 increases to that enormous organ, the cerebrum, which in man 

 fills almost the entire skull. 



I will illustrate the palaeencephalon by reference to a figure of the 

 brain of Chimaera monstrosa. This fish in reality possesses 

 nothing but the palceencephalon. From the nasal cavities in front, 

 the olfactory nerves lead into the olfactory lobes and terminate 

 there. Behind and above the olfactory lobes lies the corpus striatum 

 covered by a thin plate whence in other animals the neencephalon 



