PISCES. 1 7 1 



VI. The abducent nerves, which innervate the external rectus 

 muscles, arise almost mid-ventrally from the anterior part of the 

 bulb. [NJB. These nerves are mentioned out of their order 

 for the sake of convenience.] 



V. The trigeminal, which, like all its successors, arises from the 

 side of the bulb, is a large nerve which has 3 chief branches : 

 a. Ophthalmic, to sensory tubes on upper side of snout ; 

 /3. Maxillary, to sensory tubes on under side of snout ; 

 y. Mandibular, to muscles of the lower jaw. 



VII. The facial nerves arise close behind the trigeminals, and 

 like them have three chief branches : 



a. Ophthalmic, which first runs parallel to the similarly named 

 division of the fifth, then fuses with it and has the same distribution ; 



J3. Palatine, to roof of mouth ; 



j. Hyoidean (post-spiracular), which runs down behind the 

 spiracle, supplying muscles, and gives off small pre-spiracular 

 branches. 



VIII. The auditory nerves run into the auditory capsules to 

 supply the membranous labyrinths. 



IX. The gfassopharyngeal nerve on each side arises just behind 

 the eighth, traverses the floor of the auditory capsule, and forks 

 over the first branchial cleft into an anterior (hyoidean) branch 

 and a posterior (branchial) branch. 



X. The vagus (pneumogastric) is a large nerve arising by 

 several roots and taking a backward course. It gives off a 

 lateral line nerve, which supplies the similarly named sense-organs, 

 four branchial nerves, which fork over the last four branchial 

 clefts, and finally divides into branches for the heart and viscera. 



The spinal nerves arise segmentally from the spinal cord, each 

 by two roots, a dorsal (upon which is a small ganglion) and a 

 ventral, which pierce the wall of the spinal canal and then unite 

 together. Each segment is supplied by the corresponding pair 

 of nerves, the fibres of the dorsal root going to the skin, those of 

 the ventral root to the muscles. The regularity is somewhat dis- 

 turbed by the presence of the paired fins, which are supplied from 

 plexuses formed by certain of the anterior and posterior nerves. 



(3) The sympathetic system consists of two longitudinal 

 cords situated ventral to the vertebral column and dilated into 

 segmentally - arranged ganglia which are connected with the 

 adjoining spinal nerves. Each cord is connected in front with 



