Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 289 



ventral surface of the ceratobranchial of the fifth arch and, sepa- 

 rating into two parts, runs distally along that bone, one part of it 

 lying ventral to the lateral edge of the transversus ventralis pos- 

 terior, and another dorsal to that muscle. It is accordingly the 

 ramus posttrematicus of the fourth vagus. From that part of the 

 nerve that lies ventral to the transversus muscle a branch is sent 

 downward along the mesial surface of the pharyngo-claviculares 

 externus and internus, which it innervates. A delicate branch of 

 this nerve could be traced forward onto the mesial surface of the 

 pharyngo-hyoideus, but whether it innervates the muscle in part or 

 in whole could not be determined. 



The large superior pharyngeal nerve runs backward along the 

 dorsal surface of the oesophagus, its course and distribution not 

 being investigated. 



The Nervus Line.e Lateralis Vagi issues, as already stated, 

 with the vagus from the vagus foramen, lying dorsal to that 

 nerve. It runs at first backward, internal to all the levator mus- 

 cles, and then backward and upward along the external surface 

 of the anterior end of the trunk muscles. As it traverses the 

 vagus foramen it gives ofif its first branch, which, as already 

 stated, turns upward along the side of the skull, enters the super- 

 ficial layers of the anterior end of the trunk muscles and reaches 

 the mesial aspect of the posterior process of the squamosal. 

 There, it separates into three or four branches. The anterior 

 one of these four branches turns forward, and entering that short 

 section of the main infraorbital canal that lies in the squamosal 

 posterior to the point where the main canal is joined ^y the pre- 

 operculo-mandibular canal, innervates organ No. 13 infraorbital. 

 The posterior branch of the nerve turns backward, and entering 

 the anterior end of the suprascapular innervates organ No. 15 

 in that bone. The remaining one or two branches separate into 

 three parts all of which enter the extrascapular, one of them in- 

 nervating the main infraorbital organ No. 14, found in that bone, 

 and the other two the two organs of the supratemporal commis- 

 sure. 



The second branch of the main nervus is an accessory part of 

 the main nerve, rather than a branch of it, for, as far backward 

 as the dissection was carried, it lies parallel to the main nerve 



