8 14 MAN 



body to tlu' mic'k'iis of Dcitcrs. Ventral to Dcitcrs' nucleus is the somcw hat 

 reduced substantia gclatinosa trigcmini (NR), and latiTal to the nuek-us 

 is a massive bundle of fil)ers constituting the restiforni hudy (ICP) about 

 to estabhsh linal connections with the cerebellum. On the outer side of 

 the restiforni l)ody is a mass of nuclear material penetrated b\ nian\ nerve 

 fibers. This is the tuberculum acusticiun (Tub) which contains portions 

 ot the ventral and dorsal cochlear nuclei together with hbers arising in the 

 cochlear division of the eighth nerve. The body of the central gray matter 

 spreads across the floor of the ventricle. The specializations in the central 

 gray substance are particularly concerned with the nuclei of the \estibu- 

 lar and cochlear divisions of the eighth nerve. The most mesial of these spe- 

 cializations is the triangular nucleus of Schwalbe ( N Sc). 



At this level, the inferior olivary body appears in all its complt'x convolu- 

 tional arrangement, showing a marked increase in volume as compared with 

 the lower primates. It is associated w ith the dorsal and mesial accessory olives 

 (DO, VO). Its fundus contains amass of heavily m\fllnized axons from 

 w hicli man\ arcuate libers pass across the midline of the raphe and make their 

 way to the restiforni body. These olivo-ccrcbellar connections are much more 

 extensive than in anthropoids. They represent the only axons entering the 

 mierior c(.Tel)ellar ])eduncle and ha\ ing diffuse distribution in tlu' \ermis and 

 lateral lobes of the cerebelluni. The circumferential zone, in contact \\ ith the 

 inferior olive, contains the central tegnu'iital tract (Ctt) which affords 

 connection between the midbrain and the mlenoi- olixe. Whether this tract 

 also has constituents which establish communication with still higher levels 

 of the neuraxis, such, for exain|)le, as the interbrain, the corpus striatum and 

 even the cerebral cortex, is a cjuestion w Inch is yet to be decided. The main 

 portion of the central tt'gmcntal tract appears to come in dirt'cl communica- 

 tion with the midbrain in the neighborhood ol the third lurxe nucleus. Some 

 of its fibers appear to enter and form part of tlu' ])osterior commissure. The 



