70 ESSENTIALS OF PHYSIOLOGY. 



end in the spinal root. The cochlear division of the eighth nerve ends 

 in two nuclei, which lie close to the restiform body, the accessory nucleus 

 on its ventral aspect, and the tuberculum acusticum on its dorso-lateral 

 aspect. The vestibular division of the eighth nerve ends partly in the 

 chief vestibular nucleus in the floor of the fourth ventricle, and partly 

 in the nucleus of Deiters, which lies laterally to the chief nucleus and 

 is distinguished by the large size of its nerve cells. 



FIG. 19. Coronal section of the pons, at its upper part. (Testut. ) 

 From Gray's Anatomy. 



1, Fourth ventricle ; 2, anterior medullary velum ; 3, mesencephalic root of trigeminal ; 

 4, nerve-cells associated with this root; 5, posterior longitudinal bundle; 6, formatio 

 reticularis ; 7, lateral sulcus ; 8, section of superior peduncle ; 9, medial lemniscus ; 

 9', lateral lemniscus ; 10, 10, transverse fibres of pons ; 11, 11, pyramid ; 12, raphe ; V, 

 exit of Vth nerve. 



Groups of nerve cells, the nuclei pontis, lie among the transverse 

 fibres in the ventral portion of the pons. These nuclei form a cell- 

 station on the path of certain tracts which connect the cerebral hemi- 

 spheres with the cerebellum. Axons from cells in the cortex of each 

 cerebral hemisphere descend to the pons, where they arborise in relation 

 with the nuclei pontis. The axons of the cells of the nuclei pontis 

 become the transverse fibres of the pons, and cross the middle line to 

 pass backwards and become the middle peduncles of the cerebellum. 



