THE GENERAL FUNCTION OF THE CEREBRUM 



665 



to assume a more diversified position in nature. This is true partic- 

 ularly of birds, their more elaborate powers being directly attributable 

 to a greater development of the corpus striatum and cerebellum. In 

 mammals, on the other hand, these bodies remain relatively small, 

 whereas the external shell of the cerebrum, or pallium, is brought into 

 much greater prominence. These differences have led to the division 

 of the contituents of the cerebrum into two groups, namely, those 

 which are intimately associated with the sense of smell, and those 

 which are chiefly concerned with vision, hearing and touch. The 



Tela choroidea ventriculi tertii 

 Body of corpus cattosum | Cingulate gyrus 

 Callosal fissure 



Splenium of corpus callosum 

 Paracentral lobule 



Intermediate mass 



Fornix 

 Septum pellucidum 



Marginal gyna 

 Cenu of corpus callosu 

 Cingulate fissure 



Central fissure 



Subparietal fissure 

 I Precuneate lobule 



Parieto-occip. fissure 

 Calcarine fissure 



Cuneate lobuli 



Lamina terminalis 



Optic recess 



Optic nerve 



Optic commissure 



Hypophysis 



Corpus mamillare 



3rd ventricle 



Cerebral pedund 



Pont 

 Suprapineal rece: 



Pineal body 

 Cerebral aquedu, 



Corpora quadrigemina 



FIG. 336. MEDIAN SECTION OF AN ADTJLT BRAIN. 



(J. Symington.) 



former are spoken of collectively as the archipallium, and the latter as 

 the neopallium. The first system is the more primitive. Its impor- 

 tance gradually diminishes in favor of the second. 



As a natural consequence of this evolution we find that the cerebral 

 hemispheres increase in volume and complexity until, in the mammals, 

 they become larger than the whole of the rest of the brain put together. 

 They overshadow the primitive olfactory apparatus completely, and 

 extend backward across the brain-stem as far as the middle of the 

 cerebellum. In this way, it comes to pass that the primitive reflex 

 cerebrum of the lower forms which is largely apportioned to smell, 



