THE CRANIAL NERVES. 



545 



within which it terminates by dividing into two main branches, the 

 temporo-facial and the cervico-facial, the ultimate branches of which 

 are distributed as previously stated to the superficial muscles of the 

 head and face (Fig. 252). 



The Pars Intermedia or Nerve of Wrisberg. The facial nerve 

 at the genu facialis, the point where it turns backward to enter the 

 aqueduct of Fallopius, presents a slight enlargement, grayish in color, 

 and in which nerve-cells are contained. This enlargement is known 

 as the geniculate ganglion. The cells of this ganglion, originally 

 bipolar, present single axons which soon divide into centrally and 

 peripherally coursing branches. The former collectively constitute 

 the pars intermedia or nerve of Wrisberg, which, entering and passing 

 through the pons, termi- 

 nates around the sensor 

 end-nucleus of the glosso- 

 pharyngeal nerve ; the latter, 

 the peripherally directed 

 branches, enter the sheath 

 of the facial and accompany 

 it as far as a point about 

 five millimeters above the 

 stylo-mastoid foramen. 



From its mode of origin 

 the nerve of Wrisberg can 

 not be regarded as an 

 integral part of the facial 

 nerve proper, but is to be 

 regarded as an independent 

 sensor nerve. As to the 

 true function and relation 

 of this nerve there is much 

 conflict of opinion. 



Branches of the Fa- 

 cial. In the aqueduct of 



Fallopius the facial gives off the following branches: the greater 

 and fe'sser petrosals, the s^apedius. and the dijjrda tympani (fig. 



2 53)- 



1. The greater petrosal nerve is given off near the geniculate ganglion. 



It then passes forward into the spheno-maxillary fossa and ter- 

 minates in the spheno-palatine ganglion by an arborization of 

 its fibers around the ganglion cells. 



2. The lesser petrosal nerve is given off at a point somewhat external 



to the preceding. It leaves the skull by a small foramen and 

 terminates in the otic ganglion by an arborization of its fibers 

 around the ganglion cells. 



35 



FIG. 253. CHORDA TYMPANI NERVE, i, 2, 3, 

 4. Facial nerve passing through the aquae- 

 ductus Fallopii. 5. Ganglioform enlarge- 

 ment. 6. Great petrosal nerve. 7. Spheno- 

 palatine ganglion. 8. Small petrosal nerve. 

 9. Chorda tympani. 10, n, 12, 13. Various 

 branches of the facial. 14, 14, 15. Glosso- 

 pharyngeal nerve. (Hirschfeld.) 



