512 THE HIGHER ANTHROPOIDS 



emancipated in some measure, and the hand is thus treixl lor jjurposes of 

 exploration and prehension in functional acti\ities not chrectl\ connected 

 with locomotion. Such specialization nnplies a greater nvvd ol mtmiate 

 cooperation between the eye, neck and apjiendicular muscles ol the lorehmb. 

 This section, being somewhat higher than the corresponding levels ol 

 the forms pre\iously illustrated, shows a slightl\ dillerent arrangement of 

 the structures bordering on the lloorol the louith \entricle. The ventricular 

 lloor is formed by the central gra\ matter m whose most mesial |)ortion 

 is the nucleus hvpoglossus (Nhy). The nuclcLis is somewhat niore clearl\- 

 delimited than in tlu' lower primates, although it has by no means the sharj) 

 demarcation seen in the higher nu'inbers ol the order. The libers ol the 

 twelfth ner\'e (Nl2) pass forward Irom the nucleus in the direction ol the 

 inferior olixary body. Tlu' nucleus is se])arated Irom an adiacent aggregation 

 of gray matter by a delinite grooxe, thi' sulcus limitans. This sulcus marks 

 the position of the dorsal nucleus ol the vagus nerve (Nvd ). At the lateral 

 border of this \agal nucleus is an o\al collection ol m\t'linized axons 

 forming the fasciculus solitarius which is surrounded by a special nuclear 

 collection, the nucleus ol the lasciculus solitarius (Nts). The caudal 

 extremity of Deiters' nucleus (ND) occupii's a lateral position beneath 

 the lloor of the \entricle. Ventral to this nuckuis is the substantia 

 gelatinosa (NR) whose outer margin is m contact with a large collection 

 of libers constituting the descending trigeminal tract (Trd). On the 

 dorsolateral aspect of the section is the compact bundle of libers lorming 

 the corpus restiforme ( Fie) whose extension cephalad as the mleriiM- 

 cerebellar peduncle serves to lorm the ultimate connection ol the lower 

 segmental levels with the cerebellum. The reticular formation (Ret) is 

 extensive but i)resents no s|X'cialized nuclear aggregations at this le\i'l. 

 Occupying its characteristic ventromesial position, the pxiamid (Py) 

 forms a fasciculus of considerable si/e which, however, seems mk'rior m 



