ORIGIN OF THE CEREBRAL NERVES. 

 Fig. 255. 



497 



Fig. 255. Transparent transverse section of the cerebellum, and of 

 the uppermost planes of the medulla oblongata of Cercocebus cinomol- 

 gus. Origin of the auditory nerve. The right half of the drawing repre- 

 sents a somewhat lower plane of section than the left. F' 4 , The fourth 

 ventricle ; RRR, the cortex of the left hemisphere, of the superior 

 vermiform process and of the inferior vermiform process of the cere- 

 bellum ; vin, the internal nucleus of the auditory nerve ; N, the raphe' ; 

 P, the pyramid ; MF, motor area of the posterior division of the me- 

 dulla oblongata seen in section ; G- V, the gelatinous substance, with 

 the ascending fasciculi of the root of the fifth ; a, fibree arcuatse con- 

 tinuous with the internal division of the peduncle of the cerebellum ; 

 U, the fasciculi of the internal division of the peduncle df the cere- 

 bellum ; St, the external division of the cerebellar peduncle (large cells 

 appearing between the two divisions) ; Br, the arm of the pons (middle 

 peduncle); Us, corpus rhomboideum ; 0, sup. olivary body; 7', inf. nucleus 

 of the facial, on the outer side of the olive, from which the roots of the 

 facial (7) proceed, and extend as far as beneath the grey floor into the 

 area of the genu of the facial ; 6, nervus abducens ; 8, auditory nerve 

 arising in 8 1 from the internaLauditory nucleus on the grey floor, in 



K K 



