CRANIAL NERVES. 281 



of which, pass to the anterior wall of the 

 spiracle and to the pseudobranch. 



8. The eighth or auditory nerve, immediately after its 



origin, enters the auditory capsule through a hole 

 in the anterior end of its inner wall,, and divides 

 into branches supplying the several parts of the 

 internal ear. 

 Slice away the auditory capsule down to the level of the 

 root of the auditory nerve, and trace the nerve into it. 



9. The ninth or glosso-pharyngeal nerve arises from the side 



of the medulla, about an eighth of an inch behind the 

 auditory nerve and nearer the ventral surface. It 

 at once enters a foramen on the inner side of the 

 auditory capsule and about the middle of its length, 

 and, passing horizontally outwards and backwards 

 along a canal in the floor of the capsule, emerges 

 at its posterior and outer angle, opposite the upper 

 end of the first branchial cleft, where it divides 

 into two branches, 

 i. The anterior or pre-branchial branch is the 

 smaller of the two, and runs down the pos- 

 terior border of the hyoid arch, 

 ii. The posterior or post-branchial branch is larger, 

 and runs down the anterior border of the first 

 branchial arch. 

 Press away the medulla from the skull-wall to see the root 

 of the nerve, about an eighth of an inch behind the auditory 

 nerve : slice away the auditory capsule horizontally to expose 

 the nerve in the canal, and then follow the branches along the 

 branchial arches. 



10. The pneumogastric nerve or vagus is a large nerve, 



which arises by a number of roots from the side of 

 the hinder part of the medulla. The root of the 

 lateral-line nerve is dorsal to that of the glosso- 

 pharyngeal. 



The vagus, accompanied for some distance by 

 the lateral-fine nerve, runs outwards and backwards 



