THE FACIAL NERVE IN THE TEMPORAL BONE. 679 



Dissection. Each student may now work on his. own side. The Dissection 

 trunk of the nerve is to be found as it leaves the stylo-mastoid 

 foramen, and from this point it is to be followed upwards through 

 the temporal bone. With this view, the side of the skull should be 

 sawn through vertically between the nieatus auditorius externus and 

 the anterior border of the inastoid process, so as to open the lower 

 part of the aqueduct of Fallopius from behind. The nerve will be 

 then seen entering deeply into the substance of the temporal bone ; 

 and it can be followed forwards by cutting away with the bone- 

 forceps all the bone projecting above it. In this last step the cavity of 

 the tympanum will be opened, and the chain of bones in it exposed. 



The nerve is to be traced onwards along the inner side of the and its 

 tympanum, until it becomes enlarged, and bends suddenly inwards genu ' 

 to the meatus auditorius internus. The surrounding bone is to be 

 removed from the enlargement, so as to allow of the petrosal nerves 

 being traced from it ; and the internal nieatus is to be laid open, to 

 see the facial and auditory nerves in that canal. 



The course of the chorda tympani nerve (branch of the facial) of chorda 

 across the tympanum will be brought into sight by the removal of J 

 the central ear bone, the incus. This nerve may be also followed 

 to the facial through the wall of the cavity behind, as well as out 

 of the cavity in front. 



The remaining branches of the facial nerve in the bone are very and other 



, f ., , ,, branches. 



minute, and are not to be seen except on a fresh piece of the skull 

 which has been softened in acid. The student may, therefore, omit 

 the paragraphs marked with an asterisk, until he is able to obtain a 

 part on which a careful examination can be made. 



The FACIAL NERVE (tig. 240, *), traverses the internal auditory Facial nerve 

 meatus, and entering the aqueduct of Fallopius at the bottom of that 

 hollow, is conducted through the temporal bone to the stylo-mastoid winds 

 foramen, and the face. In its serpentine course through the bone, ^moor-ai 

 the nerve is first directed outwards to the inner wall of the bone, 

 tympanum ; at that spot it bends backwards, and is marked by a is marked 

 ganglionic swelling geniculate ganglion, with which several small w 

 nerves are united. From this swelling the nerve is continued at off twigs, 

 first backwards and then downwards through the arched aqueduct, 

 to the aperture of exit from the bone. 



The brandies of the nerve in the bone serve chiefly to connect it 

 with other nerves ; but one supplies the tongue, and another the 

 stapedius muscle, but the branches marked thus * will not be seen 

 except on a specially prepared part as described on p. 812. 



* Connecting branches unite the facial with the auditory and Branches 

 glosso-pharyngeal nerves, with Meckel's ganglion, and with the nerve 

 lingual branch of the inferior maxillary nerve. 



* Union with the auditory nerve. In the bottom of the meatus to auditory, 

 the facial and auditory nerves are connected by one or two minute 

 filaments. 



Connecting branches of the geniculate ganglion. From the con- 

 vexity of the swelling on the facial nerve three small branches 



