36 



FHE LOWER PRIMATES 



the line of demarcation between the pons and the oblongata giving rise to 

 the bulbopontile sulcus. 



At the point where the ventromedian sulcus meets the bulljopontile 



iw^ 



S; 



FIG. 18. LEFT LATERAL SURFACE OF BRAIN, LEMUR MONGOZ. 

 [Actual Length, 45 mm.] 



Key to Diagram, c, Sulcus Centralis; SULC. orb., Sulcus Orbitalis; si lc. temp, sup.. Sulcus 

 Temporalis Superior. 



sulcus, there is a small bHnd pocket underlying the pons, the foramen cecum 

 posticum. In the sulcus between the inferior olive and the pyramid the 

 twelfth nerve emerges from the oblongata (Fig. 20). 



The Pons Varolii. Continuing further cephalad, the l)rain stem is 

 characterized by the presence of a relatively narrow and flat transverse 

 band, the pons Varolii, lying in front of which is the optico-peduncular space. 

 This space is bounded cephalically by the optic chiasm and optic tracts, and 

 caudally by the convergent fdjcrs of the cerebral peduncles. It contains the 

 tuber cinereum, the region of attachment of the infundibular stalk, the 

 postinfundibular eminence and the mammillary bodies. 



A fairly well-pronounced median groove in the pons marks the position 

 of the basilar artery. 



In general, the degree of prominence attained by the pons Varolii has 

 been regarded as indicative of neopallial development. The pons provides 

 ultimate connection between the cerebral cortex and cerebellum, and is 



