SIMIA SATYRUS, THE ORANG-OUTANG 513 



voluiiH' to this structure ui the still hiyluT primates. This bundle gives 

 the nnpression that thi' orang is an animal less e\tensi\ily proNicled with 

 voluntary control o\er the somatic musculature than its higlu'r congeners. 

 Dorsal to the pvranucl aw the compact bundles constituting the mesial 

 lillet I Ml) paralleling which the lihers of the twelfth ner\e pass forward, 

 many ol them to penetiate tlu' mft-rior olisary body. 



LE\ EL OF THE \ES'ni5L LAR NLCLEI ( FIG. 233) 



At the le\el ol the \estibular nuclei, which is somewhat higher than the 

 corresponding sections in the otlur forms, the princi]>al feature appears in 

 the nuclear coniplcx related to the balancing mechanism, as it recei\'es libers 

 Irom the utricle, saccule and semicircular canals. This complex is torn- 

 posed ol the \estibular nuclei. The nucleus of Schwalbi' (NSc) lies in 

 intimate relation with the lloor of the- fourth \entricle. It has its usLial 

 triangular outline, but is less well delined than the structures lateral to it. 

 The nucleus ol Deiters (ND) is t\pical in its ajjpearance, consisting of 

 nuclear substance dispersed throughout which are numerous small bundles 

 ol myelimzed axons. Lateral to Di'itt'rs' luicleus is tlu' corpLis restiforme 

 (ICP) which passes cephalad as the interior cerebellar peduncle. 

 Bordering upon its lateral surface is the mass of gray matter constituting 

 tlu' tub(.'rculum acusticum iTub), connected with the cochli-ar di\ ision 

 ol the eighth ner\e (N8), the libers ol which penetrate this eminence. 

 Ventral to Deiters' nucleus is the substantia gelatinosa (NR) sur- 

 rounded on Its outer surlace by the t'ompact bundles lorming the descending 

 trigeminal tract (Trd). Entrant root libers ol the \estibular di\ision of 

 the eighth nerve pass either through the substantia gelatinosa or between 

 it and the corpus restiforme on their way to Deiters' nucleus. The prominence 

 ol the \estibular area as it appears in ri'liel in the lloor ol the lourt h \ en t ride, 

 as well as the dimensions of these two nuclear structures seen in cross section, 



