TROGLOD^TES NIGER, THE CHIMPANZEE 591 



which charactenzc man rniu-i'rns another tli-paiinu-nt of its neural organiza- 

 tion. That it Is ])()tc'ntiall\ ec|uippi'c[ witli and often docs df\rlo|) a surprising 

 degree ol sueh museuhir regidatioii is a fact concerning whieli tliere ean be 

 no possible doubt. 



The et'iitral gra\ matter lorining the lloor of tln' fourth \ entriele contains 

 the triangular nucleus of Sehwalbe, lateral to which is Deiters" nucleus. 

 Manx libi'is of tlu- \estibular di\ision of the eighth ner\e enter the latter 

 nucleus. X'entral to Deiters" nucleus is the substantia gclatinosa trigeiiiini, 

 in contact by its outer margin with the compact bundle forming the descend- 

 ing trigeminal tract. Contiguous w ith tlu' outer margin of this tract and w ith 

 Deiters' nucleus is a dense mass of mxelinated hbers forming the restiform 

 bod\-, while u[;on the outi'r edge ol this structure ai)pears the tuln'rculum 

 acusticum (Tub), into which man\ libers of the acoustic di\ision of the 

 eightii nerve are entering. Upon the ventral surface of the section some 

 ot tht' leatures constituting the pons \ arolii ha\e become apparent. These 

 consist ol transxcrsc libers ot the stratum superliciale surrounding a small 

 scattered mass ol nuclear substance, the pontile nuclei (PN), together 

 with the teiuk'ncx' oi the pyramidal tract to become disst'minated l)\ the 

 inter])osit ion ol nuclear substance and trans\erse j)ontile libers. 1 he boundary 

 between the basis and the tegmentum is indicated, as at higher levels, by the 

 tendenc\ of the mesial lilKt 1 Mf ) to dispose itself transversely and thus 

 serve as the line ol demarcation belwi'cn these two portions of the stem. 

 Passing through the basis jxmtis, peiu-trating both the pontile nuclei and the 

 pyramid, are some of the emerging libers of the alxlucens nerve (N6). The 

 cephalic tip ol the inferior olivary nucleus occupies a position near the center 

 ol the reticular lormation ( Ref ). The oli\-arv nucleus is in relation to the 

 dense bundle of fibers along its \entrolateral aspect constituting the central 

 tegmental tract fCtt) which serves as a connection between the olive and 

 centers in the midbrain. 



