THE ENCEPHALIC OR CRANIAL NERVES 



643 



group of cells situated beneath the floor of the fourth ventricle near the 

 median line between the nucleus of the facial and the nucleus of the motor 

 root of the trigeminal nerve and known as the nucleus salivatorius. The 

 afferent fibers arise from nerve-cells composing in large part the ganglionic 

 enlargement found on the genu of the facial nerve at the point where it turns 

 backward to enter the aqueduct of Fallopius. The cells of this geniculate 

 ganglion, originally bipolar present single axons which soon divide into 

 centrally and peripherally coursing branches. The centrally coursing 

 branches constitute in part the nerve of Wrisberg, which entering and pass- 



FIG. 267. DIAGRAM SHOWING THE BRANCHES OF THE FACIAL NERVE, THEIR RELATIONS 

 TO IT AND TO THE TRIGEMINAL AND GLOSSO-PHARYNGEAL NERVES. 



ing through the pons terminates directly or indirectly around the sensor 

 end-nucleus of the glosso-pharyngeal nerve. The peripherally coursing 

 branches enter the sheath of the facial nerve and accompany it as far 

 as a point about 5 millimeters above the stylo-mastoid foramen. 



From its mode of origin, the nerve of Wrisberg cannot be regarded as 

 an integral part of the facial nerve proper, but must be considered as an 

 independent nerve composed of both afferent and efferent fibers. 



At the beginning and in the course of the aqueduct of Fallopius the 

 facial trunk gives off the following branches: the large superficial petrosal, the 

 small superficial petrosal, the stapedius and the chorda tympani (Fig. 266). 

 i. The large superficial petrosal nerve is given off near the geniculate gan- 

 glion. It then passes forward into the spheno-maxillary fossa and be- 



