CoGHiLL, Cranial Neii'es of Aniblystovia. 225 



the lateralis component of the truncus infra-orbitalis. It inclines 

 more dorsad than the latter nerve and turns cephalad about the 

 border of the temporalis muscle. Its further course is subcu- 

 taneous, mesially of the eye, to the tip of the snout. There ap- 

 pears to be no constant manner of branching, but numerous 

 twigs arise all along its course and go to sense organs arranged 

 over, and on either side of, the main nerve. It is a purely lat- 

 eral line nerve. 



zj.. — The TnincHs MandibuLatis V. 



The mandibular trunk of the trigeminus arises from the 

 dorso-lateral portion of the Gasserian ganglion and from the 

 motor V root. The direction of the earlier part of its course 

 varies with age. In the adult it inclines caudad; in the larvae, 

 cephalad. In either case it at first lies between the masseter 

 and temporalis muscles, to both of which it sends large motor 

 twigs (not figured). 



While passing between these two muscles, the mandibular 

 ntrvQ givQs o^ lis fi]^st aitaneoiis branch {mbd. /.). This branch 

 passes latero-dorsad across the lateral aspect of the truncus infra- 

 orbitalis, then caudad over the lateral aspect of the masseter 

 muscle and m. depressor mandibulae, and some distance caudad 

 beyond these muscles. It is distributed to the skin over the 

 parts mentioned. 



The mandibular nerve now penetrates the m. masseter and 

 emerges subcutaneously laterally of the muscle, in the region 

 of the mandible. In this vicinity the nerve divides in an irreg- 

 ular manner. A nerve of considerable size, the second c^Uancons 

 branch (nibd. 2.), may arise within the m. masseter and emerge 

 from it independently, or it may arise after the main nerve has 

 emerged from the muscle. It sends one or more twigs to the 

 skin about the angle of the jaw, and another (7nbd.2.a.) ceph- 

 alad to the inner epithelium of the cheek. 



On approaching Meckel's cartilage the mandibular V 

 sends off its tht'rd cutaneous branch [iJibd.j.). This passes 

 cephalad laterally of the ramus of the jaw, at first dorsal then 

 ventrally of the r. mentalis externus VII. These two nerves 



