TROGLODYTES NIGER, THE CHIMPANZEE 603 



hands of Prolt'ssor Kiihlrr, ha\c clclmitclx disclosed the lact that the t'hmi- 

 panzcc is able to employ stereoscopic lusion elli'etix el\ . In eonjunetion witli 

 the extensne oeuloinotor eoniieetion hetween the two nuclei, this fact <z;()cs 

 a long way to substantiate the theory athanced concerning the Innction of 

 this decussation. 



On the boundarx line betwe.Mi tht' basis and tegmentum is a massive 

 aggregation of gray matter which extends Irom the lateral pt'ripher\ u lu're 

 it appears to l)c in continuitx with the mesial geniculate body (Mgb) 

 transversely across the section to the margin ol the optieo-i)eduncular s[)ace. 

 This is the sul)stantia nigra (Sbn ) the luiu'tional signihcance ot which is 

 not altogether clcarl\ understood, but to which is attributed the lunction 

 ol control o\cr automatic associated moxcmcnts. \\ hate\er its functional 

 capacity ma\' be, it is clear m the ascending series ol the primates, that the 

 nuclear structure becomes more dehnitely outlined but somewhat smaller 

 in size. The reticular formation (Ref) contains at this level a highly 

 specialized nuclear structure situated near the midluu-. This is the nucleus 

 ruber (NRu), the way-station in the pathwax out of the cerebellum which 

 serves in the capacity ot eon\eving impulses to the musck's necessary to 

 coordinative control. Its large size and clear delimtion ol outline in chim- 

 panzee indicate a strLieture engaged in functional acti\ities ol the greatest 

 importance. In contrast with the similar nucleus m the lowt'r primates, as 

 well as in the internudiate group, the red nucleus has increased both in size 

 and in clearness of dcTmition. 1 his, so lar as the chimpanzee is concerned, 

 would indicate (K'limte augmentation in the lunction ol muscular coor- 

 dination. Such interpretation is in keeping with the lact that the dentate 

 nucleus has similarly increased m this species. 



The basal ])ortion of the axis consists of a dense medullar\- structure 

 constituting the cerebral peduncle (CP) and containing heavil>- mxelinizcd 

 fibers of the jjallio-ponto-ccrcbcllar and the pyramidal systems. I-rom its 



