TROGLODYTES NIGER, THE CHIMPANZEE 571 



THE CEREBELLUM 



The cnt'ljillum presents its usual cli\ isioiis and surlaccs. The tentorial 

 surface is clist nKtl\ more gabled than is the case ol gorilla, though sonu'w hat 

 less than ni the baboon or niaeacus. The supt'rior \erniis appears as a definite 

 ridge-pole and rs partieularl\ pronounced at its cephalic e\treniit\', which 

 impresses itsell upon the unck-rsurlaci' ol the heniis|)here in the i:)OStsplenial 

 fossa. The ct'rebellar lolia pass without interruption Ironi the tentorial sur- 

 face ol the \erniis to the tentorial surlace ol the latt'ral lobes. 1 lu-se lattiT 

 structures are h'ss extensnc than 111 gorilla. The posterior notch oi tln' cere- 

 bi'llum IS present but has not attained the depth characteristic ol man. 

 U|)on the occipital surlace the mlerior \c-rmis is still a notable leature. It 

 has not been so much submerged by the t-\pansion ol the lateral lobes as m 

 the case of the human and gorilla brains. It is separated Irom t lu' lateral 

 cerebellar expansions by two vermolateral sulci which somewhat mti'rrupt 

 the passage ol the lissLires Irom the median portion to the lateral lobes. 

 The petroso-Ncntricular surlaix' ol tlu' cerebellum shows little that is dis- 

 tinctive 111 chimpanzee. The \entriciilar portion occupies a position in rela- 

 tion to the roof ol tht- fourth \eiitricle. The sui^erior \i'rmis in this region 

 projects much higher than in the lasi' ol citlu'r man or gorilla. Tlu' petrosal 

 portion IS occupied b\ the cerebello-pont ile aiigli' m which is lodged a 

 llocculus which is rt'lativelx small. .As a whole, the cerebellum, both in lorm 

 and dinu'iisions, apjjcars to be mti-rnu-diatc between that ol man and gorilla 

 on tlu' one hand, and the intermediate primates on the other. 



rHE BRAIN STEM 



The OBLONGArA. The markings on the l)rain stem in the chim|3aiizec 

 arc, if aiuthing, somewhat less delined than might be expected Irom the 

 prominence of the landmarks of the hemispheres. The oblongata uixm its 



