PITHECUS RHESUS, MACACUS RHESUS 



361 



the tail and leg, require more extensive relay stations for the eonduction of 

 sensory impulses to the brain. 



The ventricular portion of the oblongata presents a characteristic 



FIG. 168. RIGHT LATERAL SURFACE OF BRAIN, MACACUS RHESUS. 

 [Actual Length 62 mm.] 



Key to Diagram, obl., Oblongata; sulcus cent.. Sulcus Centralis; sulc. occip. lat., Sulcus Occipi- 

 talis Lateralis; sulc. precnt. inf., Sulcus Precentralis Inferior; sulc. retrocent. inf., Sulcus Retro- 

 centralis Inferior; sulcus sim., Sulcus Simiarum. 



arrangement, in the divarication of the alar plates and the opening oi the 

 ventricular space. The caudal angle is directed downward and covered for a 

 short distance by a remnant of the central gray matter, the obex. The iloor 

 of the ventricle is bounded caudally by two high walls produced by the ele- 

 vations of the cuneus and clava. These, however, gradually become reduced 

 in height until they reach the level of the lateral recess, where they are on the 

 same plane as the ventricular Iloor. This Iloor is divided longitudinally by a 

 deep median sulcus. Upon either side of this sulcus, in the lower angle oi the 

 ventricle, is the trigonum hypoglossi in the position of the hypoglossal 

 nucleus, and lateral to it, the sulcus limitans separating the trigonum hypo- 

 glossi from the fovea vagi, the latter marking the position of the dorsal vagal 

 nucleus. No area postrema or area plumiformis could be discerned in the 

 specimens examined. 



