124 



THE NERVOUS SYSTEM 



peduncle, and finally enter the corresponding hemisphere of the cerebellum 

 (Figs. 83, 86). This transverse band of fibers, which gives the bridge-like 

 form from which this part derives its name, belongs to the basilar portion of 

 the pons and is superimposed upon a deeper dorsal portion that may be regarded 

 as a direct upward continuation of the medulla oblongata. The transverse 

 fibers form a part of the pathway connecting the cerebral hemispheres with the 

 opposite cerebellar hemispheres; and the size of the pons, therefore, varies with 



Anterior limb of 

 internal capsule 



Head of the can- ' 

 date nucleus 



Anterior commissure'' 

 A nterior perforated . - 

 substance 



Optic nerve ' 

 Basis pedunculi' 



Pons 



Nervus jportio minor 



trigeminus \portio major 



Acoustic nerve 



Facial nerve 



Glossopharyngeal and vagus nerves 

 Olive 



Hypoglossal nerve 



Ventral external arcuate fibers 



Pyramid 



Ventral root N. cero. I 



Anterior lateral sulcns 



Ventral root N. cerv. II ~ 



rr~^^^---s Corona radiata 



Tail of the caudate nucleus 

 Lenticulotha- 



lamic part Posterior 

 Retrolenticular limb of 



part internal 



Sublenticular | capsule 



part J 



Thalamus 



Medial geniculate body 

 -- Superior colliculus 



" ^Inferior quadrigeminal brachium 

 "" Inferior colliculus 

 " - Trochlear nerve 

 - - Lateral lemniscus 



- - Brachium conjunctivum 

 ^~* Fila later alia pontis 

 ,> Dentate nucleus 

 Restiform body 

 Brachium pontis 



~~ ~~ Dorsal cochlear nuc. 

 ~~ Corpus pontobulbare 

 " Restiform body 

 ~ Tuberculum cinereum 

 * Accessory nerve 



--'"Dorsal root N. cerv. II 



Fig. 88. Lateral view of human brain stem. 



the size of these other structures. It is instructive to compare the brains of 

 the shark, sheep, and man with this point in mind (Figs. 11, 84, 85). 



The ventral surface of the pons is convex from above downward and from 

 side to side and rests upon the basilar portion of the occipital bone and upon 

 the dorsum sellae (Fig. 81). A groove along the median line, the basilar sulcus, 

 lodges the basilar artery (Fig. 86). 



The trigeminal nerve emerges from the ventral surface of the pons far lateral- 

 ward at the point where its constituent transverse fibers are converging to form 



