RECONSTRUCTION OF TROGLODYTES GORILLA 687 



The nuc'lrus ol the substantia (ichitinosa trim'mini, in the lower pontile 

 levels, presents the eonstrietion lounci m tlu' other primate forms — the 

 so-eallecl waist ol the tri^t-niiiial nueleiis. I he nuelear mass eontimu-s upward, 



FIG. 312. \E.\TRAL SLKKACE OF GRA^MATTER OF BRAIN STEM, 

 TROGI ODYTES GORILLA. 



Key TO Diagram, im-. oi.ive. Inferior Olive; lat. gen. body. Lateral Geniculate Body; meso-gen. body. 

 Mesial Geniculate Body; pontile, Pontile Nuclei; ret. form.. Reticular Formation; subst. nigra.. Sub- 

 stantia Nigra; vent, cocml.. Ventral ('oclilear Nucleus; \ i :n. (;i<av col.. Ventral Gray Column. 



presenting upon its lateral surfaee the cleseencling root oi the trigeminal 

 nerve, to tlu' mid-pontile region, at whieh point it t'x[)ancls into its eaput. 

 It is here in close relation with tlu' nuekus masticatoruis whieh is situated 

 mesial to the trigeminal eaput. Throughout its entire extent tlu' mesial aspect 

 of the substantia trigemini rests in a cleej) eonea\ ity formed in the lateral 

 surtaee ol tlu' retieular lormation. 



Thl Inferior Or ivarv Nucleus 



1 he interior oli\arv nueleus first apjK'ars somewhat below the le\el of 

 the opening of the iourth \entriele. Its eaudal extremity consists oi the chief 



