ORIGIN OF THE CEREBRAL NERVES. 493 



that they arise in a fine brush-like expansion from the eminentia 

 teres. 



The roots of the facial nerve have a multiple origin, which 

 will be most readily understood from the following division : 



Fig. 254. 



Fig. 254. Transparent transverse section from the pons of Man, at 

 the planes of origin of the facial and abducent nerves ; the right half 

 represents a somewhat higher plane of section than the left. Cbl, 

 Cerebellar mass forming the roof of the fourth ventricle ; Zc, the 

 projection of the internal division of the peduncle of the cerebellum 

 as it passes from the cerebellum ; Or, the projection of the corpus resti- 

 forme from the cerebellum ; R, the raphe' of the posterior division of 

 the pons ; VS, the transverse section of the motor portion of the 

 same ; /S, the transverse section of the sensory portion of the same, 

 containing the ascending roots of the fifth ; 0, the superior olivary 

 body ; Br, the brachium of the pons ; Trp, its deep, Trs, its superficial 

 layers of transverse fasciculi ; P, the anterior longitudinal fasciculi of 

 the pons ; 7, the roots of the facial nerve ; G-, the genu of the facial 

 nerve ; 7 1 , the posterior (superior) nucleus of the facial, or nucleus 

 common to the facial and abducens ; 7 2 , the anterior (inferior) nucleus 

 of the facial ; 6, root of the abducens ; 8, region of the internal audi- 

 tory nucleus in the transverse section of the grey floor of the fourth 

 ventricle. 



1. Roots of the facial, the nucleus of origin of which is 

 situated above their plane of emergence. Descending roots. 



