364 THE INTERMEDIATE PRIMATES 



The Pons Varolii. Upon the ventral surface of the brain stem the 

 oblongata is separated from a broad and Hat band of transverse nerve 

 fibers, the pons Varolii, by a well-dehned bulbopontile sulcus, which latter 

 marks the point of emergence from the brain stem of the sixth, seventh and 

 eighth nerves. The prominence of the pons denotes the degree of development 

 in the cerebral cortex, especially the neopallium, both as to its general pro- 

 portions as well as the richness of its convolutional and lissural patterns. 

 From the functional standpoint such a pontile development justities the 

 conclusion that macacus is an animal endowed with a rather extensive range 

 of skilled performances; and furthermore, capable of acquiring many learned 

 reactions quite unknown in many of the lower primates. Indeed, such promi- 

 nence in the pons bespeaks an animal capable of more complex behavior than 

 its next lower congener, the baboon. This seems to be borne out b\ the 

 reactions of these animals observed in captivity. The antagonism and stub- 

 bornness of the baboon in resisting attempts to teach it are in marked con- 

 trast to the rapid, almost uncanny acc[uisitiveness of the macacus tribes in 

 learning new, if often most aggravating tricks. 



The ventral surface of the pons presents a fairly deep groove which 

 contains the basilar artery. This surface terminates abruptly at its 

 cephalic limit in the pontopeduncular sulcus where the cerebral peduncles 

 begin. By their divergence, these peduncles create the interpeduncular 

 space, which is limited above by the optic chiasm, and bounded laterally 

 by the two cerebral peduncles and optic tracts. It contains the mam- 

 millary bodies, the region of attachment of the infundibular stalk and the 

 tuber cinereum. 



The Cerebral Peduncles. The cerebral peduncles, as is the case of 

 the pons Varolii, are more clearly defined than in the lower species, and this 

 distinctness gives the impression of an animal possessed of more discretely 

 organized behavioral reactions. This feature is of importance as it is one of the 



