194 LECTURE VIII. 



dorsal roots may be traced receding from tlie ventral ones, as they 

 penetrate the medullary substance. The hinder roots in the Blenny 

 join the facial and glosso-pharyngeal. Of the five roots of the tri- 

 geminal in the Sturgeon, the first, second, and fourth form a ganglion 

 Gasserianum. In most Osseous Fishes the first branch is sent back- 

 wards, to form, in conjunction with a branch of the nervus vagus, the 

 so-called ' nervus lateralis,' which escapes by a foramen in the parietal 

 bone ; the rest of the fifth emerges from the skull by a hole (Carp), 

 or a notch (Cod), of the alisphenoid. The lateral nerve in the Cod 

 receives only a slender filament of the vagus : it sends oif a branch 

 which runs along the sides of the interneural spines {fig. 56. I.), 

 receiving branches from all the spinal nerves : it tlien curves down 

 along the scapular arch, gives branches to tlie pectoral and ventral 

 fins, supplies the great lateral muscular masses and the mucous canal, 

 and sends a nerve along the interhtemal spines, which communicates 

 with filaments from the corresponding spinal nerves : both interneural 

 and interha^mal branches terminate in the spinal plexus supplying 

 the caudal fin : thus all the locomotive members are associated in 

 action by means of the nervi laterales.* The mandibular division of 

 the fifth (r. mandibulai'is, seu maxillce iiiferioris), consists chiefly of 

 motory filaments which supply the muscles of the hyoid and mandi- 

 bular arches, and send the ' ramus opercularis seu fiacialis,' to those of 

 the gill-cover : the sensory filaments supply the teguments of the sides 

 of the head and under jaw, enter the dental canal, supply the teeth, and, 

 in the Cod, the symphysial tentacle. The maxillary division (?•. max- 

 illaris) bifurcates behind the orbit, one branch passes outwards to 

 supply the suborbital mucous canals and integuments on the sides of 

 the head ; the other, after sending a branch obliquely outwards, curves 

 forwards along the floor of the orbit, gives ofi" a palatine nerve (r. 

 pterygo-palatinus), and supplies the integuments, mucous tubes, and 

 teeth of the upper jaw : the supra-orbital division gives off the two 

 ciliary nerves, one of which joins the ciliary branch of the third : it 

 then supplies the olfactory sacs, and the integuments of the upper and 

 fore part of the head. 



In the Skate the large sensory branches of the fifth, sent to the 

 integuments and to the singularly developed mucous canals, have 

 ganglionic enlargements near their origins where they leave the main 

 trunk. The first electric nerve is given off by the non-ganglionic 

 part of the fifth in the Torpedo (fig. 45. s), and many of the terminal 

 filaments of the tegumentary branches of the fifth swell into peculiar 



* See the beautiful figure given by Mr. Swan of this nerve in liv. pi. vii. 



