86 THE NERVOUS SYSTEM OF THE FROG. 
contact with the root of the facial nerve: it enters the 
auditory capsule and ends in the internal ear. 
9, The glossopharyngeal nerve; arises from the side of the 
medulla behind the auditory nerve, by a root common 
to it and to the tenth nerve: leaves the skull by an 
aperture immediately behind the auditory capsule, and 
divides behind the capsule into two branches :— 
i, The ramus anterior: runs downwards and _ for- 
wards round the hinder border of the auditory 
capsule and beneath the depressor mandibuli 
muscle to join the facial nerve just after it has 
crossed over the columella, 
The dissection already made for the ramus hyomandibularis of 
the facial nerve will show also the above branch of the glosso- 
pharyngeal. 
ii. The ramus posterior: runs downwards and _for- 
wards to the ventral wall of the pharynx, passing 
beneath the fourth division of the petrohyoid 
muscle but superficial to the others; it runs 
just behind and parallel to the anterior cornu of 
the hyoid. On reaching the floor of the mouth 
it crosses obliquely dorsad of the hypoglossal or 
first spinal nerve, and then runs forwards in a 
peculiarly sinuous course, close to the middle 
line and between the geniohyoid and hyoglossus 
muscles, to the base of the tongue which it enters 
and in which it ends. It supplies the petrohyoid 
muscle, and the mucous membrane of the pharynx 
and tongue. 
The dissection of the first part of the nerve is best performed 
from the side, and is much facilitated by distending the esophagus 
and pharynx with a cork or roll of paper. Its course along 
the floor of the mouth to the tongue should be dissected from the 
ventral surface. 
10. The pneumogastric or vagus nerve: arises, as already 
noticed, in common with the glossopharyngeal. It 
leaves the skull by the same aperture as the ninth nerve, 
and immediately outside the skull presents a ganglionic 
enlargement : it gives off dorsal branches to the muscles 
