THE CRANIAL NERVES. 85 
wards 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 
eyeball and its muscles, and running parallel to and a short 
distance from the skull wall. Trace rt 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 membrane and to the articulation of the 
mandible. It then divides into two branches. 
The dissection of this nerve, which is not easy, may be performed 
thus :—remove the shoulder-girdle of one side ; also the depressor 
mandibuls and temporalis muscles: open the cranial cavity as before, 
to expose the brain ; remove the tympanic membrane and clean the 
outer end of the columella. Cut away carefully 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 audrtory capsule and in close contact with rt, and trace tt back 
over the columella and down to the angle of the mouth. 
a, The ramus mandibularis; runs forward in 
the floor of the mouth, lying along the inner 
edge of the lower jaw and between the 
mylohyoid muscle and the skin, as far for- 
ward as the chin. 
Dissect from the ventral surface ; remove the skin from the under 
surface of the floor of the mouth and find the nerve running along 
the inner border of the mandible. 
(. The ramus hyoideus: the posterior and larger 
of the two branches: runs forward in the 
floor of mouth along the anterior cornu of 
the hyoid, supplying its muscles. 
8, The auditory nerve: the nerve of hearing: arises from 
the side of the medulla immediately behind and in‘close 
