674 THE IIK.HER ANTHROPOIDS 



ascending axons subst'C|iKntl\- lorm the lateral (auditory) fillet. The out- 

 standing feature of this level is the size of the pontile luielei. These nuelei 

 in gorilla, as in all of the great anthropoids and man, are so exuberant in 

 their development as to rec[uu"e an extension l)eyond tlu' pout ik' segments 

 of the axis w hieh usually suffice to contain them. Their eaiidal continuation 

 projects into the ventral surface of the pyramid in the oblongata. The exten- 

 sion ol the pontile nuelei beyond the actual metencephalie hmits denotes an 

 increment in the functions of the pons which appears striking when the gorilla 

 is compared with the l()\\er iorms. 



The heavy masses of mcdullated fibers flanking the ventricular walls 

 are composed of axons of the middle and superior cerebellar peduncles 

 (Mcp, Sep). They furnish a good index as to the richness of connection 

 between the cerebellum and other segments of the central nervous svstem. 



-e> 



LEVEL THROUGH THE AHDDLE OF THE PONS VAROLH (fIG. 306) 



Here the contour of the cross section has been materially altered by the 

 central addition of the massive structures iorming the pons Varolii. The three 

 characteristic pontile layers dilfer from those encountered in the lower and 

 intermediate primates in the greater complexity ol their several strata. 

 There is a marked increased depth in the stratum superficiale, while in 

 the stratum complexum there are more libers and a greater nuclear 

 mass constituting the pontile nuelei (PN). The stratum prohmdum 

 is also of greater depth. The libers of all tlux'i' strata become conlluent 

 to form a more extensive middle cerebellar |)edunele 1 Mcp). Scattered m 

 the midst of tlu' stratum complexum iivv the libers of tlu' pyramidal system 

 (Py) which, however, a|)pear in mueh more disseminated arrangement 

 because of the greater complexity of the nuclear mass, and the decussat- 

 ing pallio-ponto-cerebillar libers. The central gray matter (Cen) now sur- 

 rounds the much reduced apjjroach to the Sylvian aqueduet. It eontains 



