THE) BRAIN. 



39S 



and the mid-brain and the overlying cerebellum. 

 The upper half of the fourth ventricle is confined to 

 its dorsal aspect; that is, between the pons and the 

 cerebellum. Viewed from the ventral surface it pre- 

 sents the appearance of a rhomboid with striations 

 that pass transversely and become constricted later- 

 ally to form the middle peduncles of the cerebellum. 



Nucleus of nerve VI. 



Restiform body. 



Arcuate fibers. 



Descending root of 

 nerve V. 



Nucleus of nerve VII- 



s\ 



' .v\ "v y : _ '- * ^ --v'jr > s'?S5SsS_ 



Middle peduncle of 

 cerebellum. 



Nuclei pontis. 



Floor of fourth 

 ventricle. 



Posterior longitudinal 

 bundles. 



Ascending root of 

 nerve VII. 



Formatio reticularis. 

 Median raphe. 



Pyramidal bundles. 



Transverse fibers of pons. 

 Fig. 273. Cross section through the lower part of the pons. 



The fifth cranial nerve, with its large sensory root 

 and its small motor root, is attached to the ventral 

 aspect of the pons, nearer its upper than its lower 

 border. The anterior pyramids seem to enter the 

 pons from below, and emerge above the pons, where 

 they become lost in the crura cerebri. 



In a transverse section the pons presents the fol- 

 lowing parts: 



