l8o NERVE COMPONENTS OF BONY FISHES. 



2. — TJie Second and Third Brariches. 



The trunk runs out under the orbit between the m. 

 rectus externus and the m. adductor arcus palatini and in 

 this position gives off a small branch of coarse and fine 

 fibres which passes laterally and slightly ventrally to the 

 skin overlying the m. adductor niandibulae {io. 2). Here 

 the branch breaks up into several twigs, some of fine fibres 

 for the skin under the eye, a coarse-fibred twig for the 

 12th organ of the infra-orbital line, which is a naked 

 papilla, and the remainder continues ventrad and caudad 

 under the skin. Having reached the opercular canal, this 

 twig enters the bony canal, having previously penetrated 

 the m. adductor mandibulae and the pre-opercular bone. 

 In the canal it divides and sends branches to the skin 

 cephalad and caudad of this point. It sends minute twigs 

 to the skin along its entire course. 



On the opposite side of the specimen figured the course 

 of this nerve is as described above except that the oper- 

 cular general cutaneous portion breaks up earlier into a 

 number of very fine ramuli, none of which could be traced 

 into the opercular canal. The fibres of these ramuli join 

 the sub-dermal plexus and lose their sheaths. They evi- 

 dently supply the same region as on the other side, but 

 by a somewhat different course. 



The general cutaneous fibres of this second branch cor- 

 respond in nature and position rather closely to the most 

 lateral one of the three accessory trigeminal branches 

 which arise from the Gasserian ganglion in the tadpole of 

 the frog (Strong, '95). 



After the separation of this second branch, the infra- 

 orbital trunk immediately divides into three divisions, all 

 of which contain both coarse and fine fibres. The ventral 



