6i8 THE HIGHER ANTHROPOIDS 



upward into the isthmus mescncephali and hc^in to disappear in their most 

 lateral and dorsal region. Their disappcaranee from this region results in the 

 coalescenee of the constituent parts ot the oeeipito-parieto-temporo-j^ontile 

 fibers. The superlieial layer gradually cHminishes. The mesial buttress then 

 continues Lipward alone for a short distance, (inall> merging with the indif- 

 ferent mterpeduncular gray matter. The deep layer ot the pontile nucleus 

 extends cephalad and at length merges with the substantia nigra. The deep 

 layer ot the jjontile nuclei is in contact with the ventral surface ot the reticu- 

 lar tormation niesially and laterally. In the mid-pontile region a separation is 

 brought about by the development ot tlie trapezoid body. 



Large spaces appear on the lateral surface of the superiicial layer ot the 

 pontile nucknis, from which emerge the bundles of the pontocerebellar fibers. 

 This breaks up the lateral surface of the pontile nuclei into an irregular 

 appearing surlace, quite unlike the relativelx smooth surface presented by the 

 superiicial layer in the lower primates in which the pallial connections with 

 the cerebellum are relatively meager. 



The Vestibl lar Complex 



This nuclear mass makes its appearance in the caudal ventricular j)or- 

 tion of the nu'dulla where it lirst assumes recogni/.able proportions as a small 



triangular mass. It is situated betwct-n the ll ■ ot the tourth ^'entriclc and 



the dorsomesial aspect of the nucleus of Cioll. in this region the vestibular 

 complex is represented lj\ the nucleus of Deitcrs. Increasing steadily in 

 lateral and xcntrodorsal extent this nucleus progressively separates the 

 nucleus of Goll from the latt'ral wall of the touith ventricle. Above the upper 

 limit of the nucleus of (ioli tlie lateral suifaee of Di'itt'rs' nucleus comes into 

 relationship with the upper portion of the nuck'us ol Burdach. Laterall\ the 

 nucleus of Deiters has a definite xxMilral piolongal ion, triangular in shape, 

 which extends lorward and lies in contact mesialU with the lateral surtace of 



