TROGLODYTES NIGER, THE CHIMPANZEE 595 



In iIk' ci'iitial iii"a\' iiiatttT winch htTc forms tin- lloor' ol tiu' louitli 

 M.'ntrK'lc IS a collection ol niTxc cells forniinti; the nucleus abducentis (Nab). 

 Into the \ent i'](.-le proiects the nodular portion ol the nilerior \'erinis, while 

 the \entriCLilar walls are marked b\ the dentate nucleus and its surrounding 

 cajjsule ol nervt' libers. \ eiitral to the teunientum, and separated Irom it by 

 the trans\ersel\ disposed libers constitutin<i; the mesial lillet ( \H ), is the 

 basis jjontis. All ol the ti"ans\-erse libers of the pons become collected to form 

 a massi\e bundle proceedinir laterally and dorsally to enter the cerebellum as 

 the micldli' cerebellar pedLincle I Mcp ). 



LE\EL THROUGH THE MIDDLE OF THE PONS \AKOLU (fIG. 265) 



Here the contour ol the section has undergone considerable modilica- 

 tion, due to the fact that the ventricle has decreased in size as the caudal 

 orifice of the Syhian aqueduct is approached. It is bounded dorsally by the 

 \ermis of the cerebellum (\ er) and laterally by the two superior cerebellar 

 l^edunclcs (Sep). The central gray matter now lorms the lloor ol the 

 \entricle and immediatelx' beneath this is a dense bundle oi myehnized 

 libt'rs which extends ti"ans\ersely and forms the genu facialis (N7), the 

 third portion ol the enurgent course ol [hv lacial ner\c'. The tegmentum 

 is bounded Neutrally by tlu' bundles forming xhc nu'sial lillet (,.Mf ) and thus 

 separated from the basis pontis, which coniprisis the characteristic i)ontiIe 

 strata already- described in this species. The traiis\'erse fibers of the pons 

 are collected laterall\ to form t he middle cerebellar peduncle 1 M cp ) through 

 which the fibers of the trigeminal nerve ( N5 ) make their way. The larger 

 division of this lu-rve is situated dorsolaterall\ and constitutes the dorsal 

 root fibers arising in the Gasserian ganglion. The\ represent dermatoinic 

 sensory areas of the head and face, supplii'd by the fifth cranial ner\e. These 

 fibers end in an irregular mass of gra\ mattt'r forming the cephalic extremity 

 of the substantia gelatiiiosa which, because of its c(jn\oluted appearance, is 



