144 DISSECTION OF THE HEAD. 



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

 facial and auditory nerves are connected by one or two minute filaments. 



* Connecting branches of the gangliform enlargement. The swelling 

 of the facial nerve receives three small twigs. One in front is the large 

 superficial petrosal nerve* (vidian) ; another is the small superficial petro- 

 sal* of the tympanic nerve ; and the third is the external superficial 

 petrosal, *, which is derived from the sympathetic on the middle menin- 

 geal artery. 



* The branch of the stapedius muscle arises at the back of the tympa- 

 num, and reaches its muscle by a special canal. 



Chorda tympani. This long but slender branch of the facial nerve 

 crosses the tympanum, and ends in the tongue. Arising about a quarter 

 of an inch from the stylo-mastoid foramen (fig. 35, 5 ), it enters the tym- 

 panum below the pyramid. In the cavity the nerve is directed forwards 

 across the handle of the malleus and the membrana tympani to the Glase- 

 rian fissure, or to an aperture on the inner side, through which it leaves 

 the tympanum. As it issues from the cavity it emits a small branch to 

 the laxator tympani muscle (?). 



Outside the skull the chorda tympani joins the gustatory nerve, and 

 continues along it to the submaxillary ganglion and the tongue (p. 102). 



The AUDITORY NERVE will be learnt with the ear. Entering the audi- 

 tory meatus with the facial it divides into two parts, of which one belongs 

 to the cochlea, and the other to the vestibule. 



OTIC GANGLION (fig. 36). At this stage of the dissection there is little 

 to be seen of the ganglion, but the student should remember that it is one 

 of the things to be examined in a fresh part. Its situation is on the 

 inner aspect of the inferior maxillary nerve, close to the base of the skull, 

 and it must therefore be arrived at from the inner side. 



Dissection. Putting the part in the same position as for the examina- 

 tion of Meckel's ganglion, the dissector should define the Eustachian tube 

 and the muscles of the palate, and then take away the levator palati anjd 

 that tube, using much care in removing the last. When some loose 

 areolar tissue has been cleared away the internal pterygoid muscle (b) 

 comes into view, with the trunk of the inferior maxillary nerve above it ; 

 and a branch (internal pterygoid, 5 ) descending from that nerve to the 

 muscle. If the nerve to the pterygoid be taken as a guide, it will lead to 

 the ganglion. 



To complete the dissection, saw vertically through the petrous part of 

 the temporal bone, near the inner wall of the tympanum, the bone being 

 supported whilst it is divided. Taking off some membrane which covers 

 the ganglion, the student may follow backwards a small branch to the 

 tensor tympani muscle ; but he must open the small tube that contains the 

 muscle, by entering it below through the carotid canal. Above this small 

 branch there is said to be another minute nerve (small superficial petrosal), 

 which issues from the skull, and joins the back of the ganglion. A small 

 twig is to be sought from the front of the ganglion to the tensor palati 

 muscle ; and one, near the same spot, to join the sympathetic nerve on 

 the middle meningeal artery. 



The OTIC GANGLION (gang, auriculare, Arnold) (fig. 3G) is a small 

 reddish body, which is situate on the inner surface of the inferior maxil- 

 lary nerve close to the skull, and surrounds the origin of the nerve to the 

 internal pterygoid muscle. By its inner surface the ganglion is in contact 

 with the Eustachian tube, and at a little distance, behind, lies the middle 



