THE CRANIAL NERVES 81 



7. The facial nerve arises from the side of the medulla 

 immediately behind the trigeminal nerve, and passes 

 forwards to the skull wall, where it is very closely con- 

 nected with the Gasserian ganglion. It passes through 

 the skull wall immediately behind and in close company 

 with the trigeminal nerve, and divides at once into its 

 two main branches. 



i. The ramus palatinus runs forwards in the floor 

 of the orbit a short distance from the side wall 

 of the skull, and immediately upon the mucous 

 membrane of the roof of the mouth. Near the~ 

 anterior end of the orbit it divides into two 

 branches, one of which runs outwards and 

 anastomoses with the ramus maxillaris of the 

 trigeminal nerve, while the other runs forwards 

 to the anterior part of the roof of the mouth. It 

 supplies the mucous membrane of the roof of the 

 mouth. 



Dissect this nerve from the ventral surface. Cut away the lower 

 jaw : carefully remove the mucous membrane of the roof of the 

 mouth, and find the nerve lying on the ventral surface of the eye- 

 ball and its muscles, and running parallel to and a short distance 

 from the skull wall. Trace it backwards and forwards. 



ii. The ramus hyomandibularis runs outwards and 

 backwards round the front end of the auditory 

 capsule ; it then crosses over the inner end of the 

 columella and turns downwards in the posterior 

 wall of the Eustachian tube to the angle of the 

 mouth, giving branches to the tympanic mem- 

 brane and to the articulation of the mandible. 

 It then divides into two branches. 



The exposure of the above nerve, which is not easy, may be 

 performed thus : remove the shoulder girdle of one side ; also the 

 dejrressor mandibulce and temporalis muscles : open the cranial 

 cavity as before, to expose the brain : remove (he tympanic mem- 

 brane and clean the outer end of the columella. Cut away care- 

 fully the roof of the auditory capsule by a horizontal cut, just 

 above the level of the columella : find the facial nerve running 

 round the front end of the auditory capsule and in close contact 



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