722 THE HIGHER ANTHROPOIDS 



hemispheres. This delegation serves the purpose of affording a w ider, more 

 ample region in the brain for auditory associations. It also firings these 

 associations into intimate rehition with afferent iinpulses received from many 

 other types of receptors in the body, and thus makes possible that blending of 

 sensory impressions w hieh forms the basis of broader experience. 



COMPARISON OF THE SUPERIOR COLLICULUS IN THE HIGHER ANTHROPOIDS 



The comparison of the superior coilieuhis in the higher anthropoids docs 

 not turnish as convincing evidence of the telencephahzation of the visual 

 function as does the interior eolhcuhis with reference to the sense ol hearing. 

 In lact, the orang-outang and chimpanzee show the greatest amount of 

 deflioresccnee in this portion of the midbrain and indicate thereby a greater 

 degree of deh'gation of function to the visual cortex in the cerebral heiiii- 

 spheres. This places the gorilla at a distinct disadvantage in the comparative 

 sense. It may be that the mode of life of these three species has some bearing 

 upon this apparent inconsistency. Both the orang and the chimpanzee live 

 among the trees, and enjoy a more unrestricted \ iew of their surroundings 

 than does the gorilla, whose visual outlook is much obstructed by the under- 

 brush. \\ hether this be regarded as a wiiolly satisfactory explanation for the 

 distinct retardation which the gorilla shows in tlu' teleneephalization ol its 

 visual function, it seems advisable to accept the coeilicients of the superior 

 colliculus as they ha\e been obtained by measurement m the iollowing 

 tabulation, witli the suggestions ollered in explanation ol them: 



