202 NERVE COMPONENTS OF BONY FISHES. 



X. — The R. Lateralis Accessorius. 



This nerve receives communis fibres from the vagus 

 and from the facialis. The latter arise from the genicu- 

 late ganglion by several small roots, which will be 

 enumerated from behind forward. The first and largest 

 of these recurrent roots [rec. i) arises from the most cau- 

 dal portion of the geniculate ganglion in several strands. 

 Their relations are indicated somewhat diagrammatically 

 in Fig. 26, which is a composite of several successive 

 camera outlines of this region. Three of them pass di- 

 rectly dorsad over the emerging spinal V root and mesally 

 of the dorsal lateral line root, while one arises farther for- 

 ward than the others from the ventral surface of the 

 ganglion and passes dorsad and caudad mesally of the 

 sensory V root just after its emergence from the oblongata 

 and of all the other V + VII roots, but laterally of the IV 

 root. This root it follows back to its origin and then 

 joins the other strands on the dorsal side of the dorsal 

 lateral line root. This strand has a double origin, the 

 two portions separately entering the IV nerve, which they 

 closely follow and from which they separate together. 

 The root as thus composed then continues dorsad into the 

 meninges at the level of the caudal end of the optic lobe, 

 then through a foramen in the cranial roof to turn caudad 

 under the skin. It is composed chiefly of very fine fibres 

 with a few more densely myelinated fibres of medium 

 size scattered among them. 



From the cephalic tip of the geniculate ganglion, after 

 the separation of the fibres which go out through the hyo- 

 mandibular foramen, the remaining communis fibres 

 divide into two bundles. The larger one goes out ven- 

 trally with the infra-orbital trunk, as already described; 

 the smaller one curves around the outer side of the 



