THE NERVOUS SYSTEM 



501 



parietal lobe are the anterior and posterior central, the superior and 

 inferior parietal, the submarginal, and the angular. The occipital 

 lobe has lingual, fusiform in part, and lateral gyri; the temporal lobe 

 superior, middle and inferior, hippocampal, and uncus. The g3n-us 

 cinguli on the median surface of the hemispheres extends through frontal 

 and parietal lobes. Covered by the parietal, frontal, and temporal 

 lobes on the lateral side of the hemisphere is an insula, the surface of which 

 is subdivided into short and long gyri. (Figs. 418, 419) 



VISUAL 



'OLFACTORY/ ^^/-^ — ^^ ^ >f ACOUSTIC - 



ACOUSTIC 



C. TARSIER. D. MARMOSET. 



Fig. 416. — Diagrams of the brains of insectivores and of lower primates viewed 

 from the left side. The figures show the increasing dominance of the centers of vision 

 over those of smell. A. Brain of Jumping Shrew. B. Brain of Tree Shrew. C. Brain 

 of the primate Tarsier. D. Brain of the Marmoset. (Redrawn after G. Elliot Smith.) 



Each lobe contains a restricted portion of a lateral ventricle. Con- 

 nexion with the third ventricle is effected by an interventricular foramen 

 or foramen of Monro. 



Corpus Striatum. The second portion of the telencephalon which 

 undergoes striking changes and enlargement in the course of phylogenesis 

 is the corpus striatum, so-called because of its striped appearance in 

 sections. This striate body or basal ganglion arises as a local thickening 

 of the ventro-lateral wall of the telencephalon. Like other parts of this 

 division of the brain, the striate body is connected primarily with olfactory 

 fibers and is an olfactory reflex center. The organ is poorly developed 

 in cyclostomes; but is a well-marked swelling in elasmobranchs, with a 

 paleostriatum and an epistriatum. (Figs. 414, 415) 



The amphibian brain, however, may be taken as the prototype of 

 the vertebrate. Each hemisphere of the amphibian brain is divided 



