466 THE INTERMEDIATE PRIMATES 



of coordinative control. Although it must be admitted that the manual difler- 

 entiation in baboon, while in some respects superior to that of gibbon, is 

 in no way better than that of macacus, nevertheless, the dual responsibility 

 forced upon the forelimbs for locomotion upon the ground and in climbing 

 entails a higher degree of specialization of coordinative control than in either 

 of the other two forms considered. Such an interpretation is none too strongly 

 urged at this time. Other factors may be operative which as yet have not come 

 to light. This explanation of the larger size of the dentate nucleus in the 

 baboon than in the other intermediate primates, however, seems for the 

 moment worthy of consideration. The coefTicients of the dentate nucleus 

 in the baboon, macaque and gibbon are given in the appended tabulation: 



Coefficients of the Dentate Nucleus in the Intermediate Primates 



It IS perhaps of even greater significance that the nucleus dentatus in 

 the intermediate primates is in all cases greater than the similar structure 

 in the lower primates. This difference would indicate a definite expansion in 

 cerebellar function in passing from these lower to the higher forms. It points 

 to a probable increment in the coordinative control of the musculature since 

 these animals are becoming more highly specialized in their motor capacity, 

 which gives them a wider range of behavioral adaptation. 



The nuclear specialization in the midbrain which receives, as a relay 

 station, the superior cerebellar peduncle, namely, the red nucleus, bears out 

 the fact already observed in relation with the nucleus dentatus. The nucleus 

 ruber is larger in the baboon than in either the gibbon or macacus, thus 



