486 FISHES. 



X. The vagus ) apparently made up of at least four 

 cranial nerves, has five 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: 



(a) A ganglionated root to the clefts and arches (2 to 5 



inclusive), with post - branchial, prae- branchial, 

 and pharyngeal branches, as in IX. 



(b] A ganglionated root, arising in front of all the 



others, from which arises the lateral branch in- 

 nervating all the posterior sensory tubes, 

 (r) From the fourth branchial branch arises the gan- 

 glionated intestinal which innervates the heart 

 and the stomach. 



FIG. 158. Side view of chief cranial nerves of Elasmo- 

 branchs. (Slightly modified from COSSAR EWART.) 



olf.) Over olfactory nerve; ck., over cerebral hemispheres; cb., 

 over cerebellum; m.o., over medulla oblongata ; ;;z., mouth; vix., 

 maxillary branch of 5 ; mn.$., mandibular branch of 5 ; vm.j., mandi- 

 bular branch of seventh nerve; #.1-5., groups of ampullae; o.s.$., 

 superficial ophthalmic of 5; o.p., ophthalmicus profundus ; o.s.'j., 

 superficial ophthalmic of 7 ; N. t nostril; 3., oculomotor ; e.g., ciliary 

 ganglion ; 5., trigeminal ; /.., inner buccal ; o.b., outer buccal ; 7.^., 

 buccal of 7 ; /, palatal of 7; sp., spiracle; ch., chorda tympani ; 

 j.hm., hyomandibular of 7 ; 8., auditory ; ., ear; 9., glossopharyn- 

 geal ; 10., roots of vagus; /.io., lateral nerve of vagus ; z'.io., intes- 

 tinal nerve of vagus ; I'-s', gill clefts. 



The spinal cord lies in the cartilaginous neural archway 

 above the vertebral column, is divided by deep dorsal and 

 ventral fissures, and gives off numerous spinal nerves, 

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



