THE ENCEPHALIC OR CRANIAL NERVES 629 



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. 270). 

 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- 

 comes associated with the spheno-palatine or Meckel's ganglion. In its 

 course it receives a filament known as the deep petrosal, from the car- 

 otid plexus of the sympathetic. The nerve-trunk formed by the union of 

 these two nerves is known as the 

 Vidian nerve and terminates as 

 stated above. The character and 

 function of the large petrosal 

 nerve have been a subject of 

 much discussion. As the out- 

 come of modern methods of in- 

 ' vestigation it may be concluded 

 that it is composed mainly, if 

 not entirely, of fine medullated 

 nerve-fibers which are the con- 

 tinuations of corresponding fi- 

 bers in the nerve of Wrisberg 

 and that their destination is 

 the spheno-palatine ganglion, FI G . 270. CHORDA TYMPANI NERVE, i, 2, 

 around the nerve-Cells of 3> 4- Facial nerve passing through the aqueductus 

 whirh their term in a 1 hranrhp*; Fallopii. 5. Ganglioform enlargement. 6. 



5 Great petrosal nerve. 7. Spheno-palatine gan- 

 arbonze. glion. 8. Small' petrosal nerve. 9. Chorda tym- 



Stimulation of the large petrosal, P a - I0 > IJ > I2 > J 3- Various branches of the 



.,1 . j j ! , . facial. 14. 14, 15. Glosso-pharyngeal nerve. 



with induced electric currents, (Hirsckfeld.) 

 gives rise to a dilatation of the 



blood-vessels of, and a secretion from the mucous membrane, of the 

 nose, soft palate, upper part of the pharynx, roof of the mouth, gums, 

 and upper lip the regions of distribution of the post-ganglionic fibers 

 of cells of the spheno-palatine ganglion (see page 647). The nerve 

 therefore contains both vaso-dilatator and secretor fibers which belong 

 to the autonomic system of nerves. As after the administration of 

 nicotine stimulation of this nerve is without effect, and as stimula- 

 tion of the spheno-palatine ganglion gives rise to the usual vaso-dila- 

 tator and secretor effects it may be inferred that the ganglion is the 

 way station between the pre-ganglionic fibers and the blood-vessels and 

 glands. The deep petrosal, which joins the large petrosal is in all 

 probability a vaso-constrictor nerve coming from the superior cervical 

 ganglion of the sympathetic. There is no evidence that the large pe- 

 trosal contains any fibers from the facial proper for the innervation of: 

 any striated muscle of the palate. 



2. The small superficial petrosal nerve is given off from the facial at a 

 point somewhat external to the large petrosal nerve. In its course 

 it is joined by a small filament derived from Jacobson's branch of the 

 glosso-pharyngeal. Together they pass into the otic ganglion, where 



