576 THE HIGHER ANTHROPOIDS 



mamniillar\ bodies, the attaclimfiit ol tin- iiilundilnilai' stalk and the tuber 

 einereuni. There are no espeeially eharaeteristic features in it to distmguisli 

 this region from that of other primates. 



Internal Structire of the Brain Stem in Chlmpanzee 

 le\el of the pyra.xhdal decussation ( fu;. 256) 



At this le\el Xhv section shows as its most conspicuous teature the decus- 

 sating libers of the p\rainidal system ( P\\ ). Oecup\ ing the usual \entro- 

 mcsial jjortion of the section are the still uncrossed p\ ramidal libers ( Py ). 

 The crossing fillers, ho\ve\er, ha\e caused a dellection ol the sulcus, and in 

 the course of their decussation have gone so far toward occupxing their 

 ultimate position in tlu' spinal cord as to ha\"e more or less completel\' 

 di-tached the xentral gray column (V'en) from the central gra\ matter 

 (Ceil). On the periplu'ry of the section certain indentures indicate the 

 position ol the major sulci on the surface ol the stem. The ventromedian 

 sulcus lias alrcad\ been referred to and tin- dellection in it caused b\ the 

 decussating pyramidal bundles. A laiiitl\ marked internu'diatc sulcus lies 

 \'cnti"al to the substantia gelatinosa trigemini ( N R ), \\hile dorsal to this 

 structure is the dorsolateral sulcus and a laintl\ indicated dorsal para- 

 median sulcus. In tlu' dorsal seiisorx lield, the columns ol CjoII and Burdach 

 are clearl\ demarcated by a dorsal paraniedian sulcus, the di\isioii between 

 tlu' two cohimns showing clearly a prepondcranei' in size which favors 

 Burdach's column ( CB ). In the column of C.oll ( CG ) the caudal extremity 

 of this nucleus may be discerned ( NG ). It is adjacent to the median septum 

 but iinested l)y a dense capsule of myelim/A'd libers. E\t("ndiiig dorsolatcrallN 

 from the central gray matter is the proximal portion of the nucleus of 

 Burdach passing outwarcf into the surrounding iiu'dullarx substance of 

 the corresponding column. A tenuous cxtinsion ol the central gray connects 

 ^vith the somewhat expaiuk'd substantia gelatinosa trigemini (NR) upon 



