THE BACK. 



415 



the floor of the fourth ventricle. It may be seen in dissection piercing the dura 

 below and internal to the fifth nerve. (Fig. 88.) In the cavernous sinus the 

 nerve lies on the outer side of and is attached to the internal carotid artery. 

 (Fig. 88.) In the sinus the sixth nerve is joined by sympathetic filaments from 

 the cavernous plexus, and receives a twig from the ophthalmic branch of the 

 fifth nerve. (Fig. 98.) 



The Seventh or Facial Nerve. (i) Leaves the cranium by the internal audi- 

 tory meatus in company with the auditory or eighth cranial nerve and the audi- 

 tory artery, a branch of the basilar artery. (2) In the internal auditory canal it 

 is connected to the auditory nerve by the pars intermedia, and enters a separate 

 bony canal, called the aqueductus Fallopii, one-quarter of an inch from the in- 

 ternal auditory meatus. (3) On nearing the tympanum the nerve turns sharply 

 backward and presents an enlargement, called the intumescentia gangliformis (gen- 



Supnavrbifal 3?! 1 



FIG. 291. SEVENTH CRANIAL NERVE, FACIAL, OR PORTIA DURA. 



Great petrosal, to form Vidian with No. 5. 2. Small petrosal, to otic ganglion. 3. External petrosal, 

 to plexus on mid-meningeal artery. 4. Tympanic branch to stapedius, etc. 5. Branch from carotid 

 plexus making Vidian, with No. I. 6, 7. Branches to auriculo-temporal of fifth. 8. Branch to 

 auricular of vagus. M. The ganglion of Meckel. O. A. F. Orifice of aqueductus fallopii. 



iculate ganglion). (4) From the geniculate ganglion are the following branches : 

 (a] The large superficial petrosal to Meckel's ganglion. This branch leaves the 

 cranium by the foramen lacerum medium, and joins a branch from the carotid 

 sympathetic plexus, called the large deep petrosal, to form the Vidian nerve. (/?) 

 The small superficial petrosal to the otic ganglion. This nerve leaves the 

 cranium by the canalis innominatus, a small opening between the foramen ovale 

 and the foramen spinosum, in the greater wing of the sphenoid bone. This branch 

 receives a communicating twig from the tympanic branch of the glosso-pharyn- 

 geal nerve, (r) The external superficial petrosal nerve, to join the sympathetic 

 on the middle meningeal artery. (5) The facial nerve traverses the middle ear 

 in its bony canal, traversing between the roof and inner wall, and between the 

 inner wall and the posterior, successively, emerging at the stylo-mastoid foramen. 

 (6) In the middle ear the nerve gives off (a] a small branch to the stapedius 

 muscle ; (b] the chorda tympani, which supplies the submaxillary and sublingual 



