836 MAN 



(Put). Other morphological features of this Ie\el are indicated by corre- 

 sponding markings which appear in the legends accompanying the frgures. 



LEVEL OF THE ANTERIOR CO.\LMISSURE (fIG. 357) 



Here the brain stem comes to its cephahc termination. The third ven- 

 tricle, less deep and somewhat broader than in the level of the optic chiasm, 

 is Hanked upon either side I^y the cephalic extremity of the optic thahimus. 

 All of the structures in this region of tlie brain in man correspond in detail 

 with the homologous elements of the lower and intermediate primates as 

 well as the great anthropoids. 



Features of Human Brain Showing Greatest 

 Evolutional Significance 



In concluding the re\'iew of the human brain, it is difficult to decide 

 which features have the greatest evolutional significance. The neopallium, 

 pons Varolii, p\ ramid and cerebral peduncle probably should be given the 

 place of first importance. The lateral lobes of the cerebellum, the dentate 

 and red nuclei, the superior cerebellar peduncle and inferior olive are but 

 little less decisive in their evidence. All of these structures are essential 

 factors in the organization and control of mammalian motor specialization. 

 Their progressive evolutionary development in the primates denotes to what 

 degree behavioral capacity has been extended. The history of these structures 

 is closely interwoven with the differentiation of the extremities and then- 

 record reveals how that process has advanced through many phases from 

 apes to man until the human hand made its appearance. This specialization 

 is the final test which ma\- be employixl to explain the extensive develop- 

 ments of the human brain. 



