CRAlflAL NERVES 247 



spiracle, where it lies just beneath the skin, 

 and then runs downwards and backwards 

 along the anterior border of the hyoidean 

 arch, giving branches to the muscles of these 

 parts. 



Close to its origin it gives off a number of 

 smaU pre-spiracular branches 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 

 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 is a slender nerve which 



arises from the side of the meduUa, about an eighth 

 of an iach behind the auditory nerve and nearer the 

 ventral surface. It at once enters a foramen on the 

 inner side of the auditory capsule, and passing hori- 

 zontally 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 hyoidean branch is the smaller 

 of the two, and runs down the posterior 

 border of the hyoidean arch. 



ii. The posterior or branchial branch is larger, and 

 runs down the anterior border of the iirst 

 branchial arch. 



Press a/way the medulla from, the shull-wall to see the root 

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

 nerve : slice away the a/uditory capsule horizontally to expose 

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

 arches. 



