SIMIA SATYRUS, THE ORANG-OUTANG 515 



tlu' p\raiiiicl ( Py). Extcnclin^^ clircctlx' l)ack\var(l toward the lloor of the 

 \fiitiick' is tlu' tlc-nse huiKllc of tlir nu'sial lillct (Ml). W-iitroiiU'sial to 

 tlic ])\raiiiicl IS a larm' (.■oHfction ol gray matter constituting the arcilorni 

 nucleus (Nar) which, in all probability, is a caudal extension of the 

 jjontile nuclei. In any east', these two nuclear structures are definitely 

 continuous, thus creating the impression that e.\|)ansions ol the nuclear 

 specializations of the pons ha\e rt'sorted to a caudal extension in order to 

 accommodate their apparently exuberant growth. 



LE\"EL OF THE CEREBELIAK NUCLEI (FIG. 234) 



At the le\el of the cerebellar nuclei the contour of the section has under- 

 gone marked alteration chielly beeaust' of the continuitx ot the stem with 

 the cerebellum b\ means of the middk' cerebellar ])eduncli' i M cp). The 

 large mass of the niedullarx xcstibule of the cerebellum ap|)ears on the 

 lateral aspect of the section and contains the somewhat conxoluted and 

 i:)oorly defined nucleus dentatus (Ndt). Mesial to it in the roof of the 

 ventricle is tlie nucleus globosus. Both the size and dehnition ol the 

 dentate nucleus, as compared with tlu' lower jjrimates, indicate an animal 

 with a greater degree of coordinati\e control over the musculature. Although 

 the increased dimensions of the dentate nucleus as comparetl with the lower 

 primates is evident, there is an ec|uall\ striking contrast when this nucleus 

 is compared w ith that of the higher forms, it then appears less well defined, 

 less i^romineiit and smaller than in t lu' other great anthropoids, implying 

 that orang is not so well ])ro\ ided in muscular coordination as those 

 primates standing above it in tin- scale. 



The central gray matter forms the lloor of the ventricle (Ven iv) 

 without special nuclear dilferentiatioii. Mesially, the posterior longitudinal 

 fasciculus comes closer to the ventricular lloor than is the case at lower 

 levels. Some fibers of the cochlear division of the eighth nerve (N 8) enter the 



