RECONSTRUCTION OF TROGLODVTFS NIGER 619 



the descending tract ol tlu' tri<;x'ininal nci\ i-. In rccnnstriictinii tlic substantia 

 gelatinosa trigcmini is in close relation with, l)Ut separated troin, the nucleus 

 of Dciters l)y a cicit in which is lodgt'cl the ck-scending root ol tlie trigeminal 

 nerve. 



In the niid-\entricular region Deiters' nucleus gradually begins to 

 diminish in size and is replaced b\ the triangular nucleus ol Schwalbe situated 

 somewhat dorsal and slightly mesial to the Deitersal nucleus. This nucleus 

 continues upward to the mid-])ontile level where it gradually dimimshes in 

 size and then disappears. The triangular nucleus is covered b\ the dorsal 

 cochlear nucleus w Inch lies iinnu'diately subjacent to tlie subej)end\ inal gray 

 matter forming the lloor of the fourth wntricle. 



Above the opening ol the lati-ral recess the nucleus of Bechterew 

 appears in the extreme dorsolateral angle of the tegmentum extending into 

 the lateral wall of the ventricular ca\ity. The entire vestibular com])K'x 

 extends cephalically as far as the upper limit of tlu' sul)staiUia gelatinosa 

 trigemini. Its ventral prolongation passes deepl\' into the tegnn'iituin ol the 

 metencephaion, approaching closely to the trans\erse plane ot the neuraxis. 



The Cochlear Complex 



The cochlear complex consists of the ventral and the dorsal nuclei 

 which are connected by strands of nuclear material. The ventral cochlear 

 nucleus is relatl\ely massi\e but not augmented in proportion to the abso- 

 lute increase in the amount of nuclear mali'rial ot the brain stem. By com- 

 parison the relati\e mass of gray matter would seem to be less than that 

 found in some of the lower forms such as the Macacus rhesus and the Cyno- 

 ccphalus babuin. The central tochkar nucleus is arranged in the usual fashion, 

 more or less trough-like in shape, enveloping the entering cochlear root on 

 its caudal, lateral and cephalic surfaces. The dorsal nucleus is relativelx 

 extensive and lies directly in contact with the subependymal gray matter 



