694 THE HIGHER ANTHROPOIDS 



The Deittrsal complex rapidly increases in size and separates the upper 

 ])orti()n ol the nucleus of Burdach from the central ^ray matter forming the 

 lloor oi the lourth ventricle. It also extends rapidly in its ventrodorsal diame- 

 ter, appearing as a wedge-shaped mass with a triangular extension which 

 overhangs the substantia gelatinosa trigemini. It is separated from the latter 

 hy the interposition of the descending root of the trigeminal nerve. 



Near the lateral recess of the fourth ventricle the Deitersal complex 

 begins to diminish in size and is replaced by the triangular nucleus of 

 Schwalbe. 



Above the region of the lateral recess the nucleus of von Bechterew 

 appears in the lateral wall of the fourth ventricle. The entire vestibular 

 complex extends upward to the mid-pontile level where it rather abruptly 

 begins to diminish and then disappears by merging with the metencephalic 

 reticular formation. 



The Cochlear Complex 



The cochlear complex consists of the ventral and the dorsal cochlear 

 nuclei. The ventral nucleus presents the regular appearance of a trough 

 receiving the entering cochlear root on its mesial surface, surrounding the 

 nerve upon its caudal, lateral and cej)halic aspects. The dorsal cochlear 

 nucleus is situated in the lateral vi'iitricular recess. It is superposed upon the 

 vestibular area and is connected w ith the \i'ntral cochU'ar nuck'us hy strands 

 of gray matter interspersed between the radicular and secondary cochlear 

 fibers. The de\ elopnu'iit ol the cochlear comph'x is about the same as that 

 found 111 the ehimpau/AX' but appears less e\ti'nsl\'e w lu'ii compart-d w ith the 

 rest of the gray matter of the stem in most of tlu' lowir primates. 



The CoLi.ici i.i 



These masses occup\ their usual positions in the tei'tuni o| the mesen- 

 cephalon. The superior colliculus is somewhat larger than tlie uilerior col- 



