CRANIAL NERVES. 541 



6. The "facial proper," apparently arising from 3, 



supplies the muscles of the hyoid arch. 



7. The "chorda tympani," apparently arising from 3, 



runs under the spiracle to the inner side of the 

 jaw. 



With the loss of the sensory ampullae, the seventh 

 nerve of higher Vertebrates becomes restricted to 

 the last three branches (5, 6, and 7). 



A recurrent branch of the facial also runs external 

 to the auditory capsule to IX., and is equivalent 

 to Jacobson's anastomosis in higher forms. 



VIII. The auditory, arising just behind VIL, is the nerve 



of the ear. 



IX. The glossopharyngeal, the most typical of all, is the 

 nerve of the first functional gill-cleft. Its root 

 passes through the floor of the auditory capsule, 

 and bears a ganglion above the cleft. Its 

 branches, as named by Beard, are : 



1. Post-branchial, to the muscles of the first branchial 



arch ; 



2. Prse-branchial, arches over the cleft and runs along 



its front wall ; 



3. Intestinal or visceral, to the pharynx ; 



4. Supra-branchial or dorsal, to a few sense organs on 



the mid-dorsal line of the head. 



X. The vagus, apparently made up of several cranial 

 nerves, has numerous roots, and divides into six 

 main ganglionated portions, which supply the 

 four posterior clefts and arches, the posterior 

 jelly-tubes, and the heart and stomach. It thus 

 consists of: 



1. Ganglionated roots with nerves to the clefts and 



arches (2 to 5 inclusive), with post-branchial, 

 prse-branchial, and pharyngeal branches as in IX. 



2. A ganglionated root, arising in front of all the 



others, from which arises the lateral branch 

 innervating all the posterior sensory tubes. 



3. From the fourth branchial branch arises the gang- 



lionated intestinal which innervates the heart and 

 the stomach. 



The spinal cord lies in the cartilaginous neural archwad 

 above the vertebral column, is divided by deep dorsal any 

 ventral fissures, and gives off numerous spinal nerves, 

 formed as usual from the union of dorsal (sensory) and 



