I02 NERVE COMPONENTS OF BONY FISHES. 



the second m. levator arcus branchii externus {2. I. a. e.) 

 and then the truncus divides into pre-trematic and post- 

 trematic rami. The former is quite small. It gives off 

 immediately a pharyngeal ramus (communis fibres) for 

 the roof of the mouth adjacent, which, though slightly 

 larger than that of the IX nerve, is nevertheless incon- 

 siderable. 



The pre-trematic ramus, upon entering the first gill, 

 takes its position on the outer or convex surface of the 

 ceratobranchial bar just above the attachment of the 

 second demibranch to the bar, where it may be followed 

 to the base of the gill. Here it joins the ventral ramulus of 

 the post-trematic IX and can no longer be separately 

 traced. This anastomosis has been found only in the first 

 gill. If it occurs at all in the others, it can involve only 

 the ultimate terminal fibrils of the pre-branchial nerves, 

 as careful examination has failed to demonstrate it. The 

 other pre-trematic branches are smaller and can be 

 traced into their respective gills a much shorter distance 

 than this one. 



The post-trematic ramus pursues a course in the second 

 gill which is substantially similar to that of the IX in the 

 first gill. The most important difference (aside from the 

 apparent absence of the anastomosis of the ventral ramu- 

 lus with the second pre-branchial) is correlated with the 

 fact that the long gill rakers of the first gill are wanting 

 in the second, their place being taken by numerous teeth 

 born on the dorsal side. To these teeth and the large 

 taste buds among them the dorsal ramulus is distributed, 

 as well as to the taste buds of the floor of the pharynx 

 near the base of the gill. The dorsal and ventral ramuli 

 are about equal in size. 



The ganglion of the first branchial nerve of the vagus is 



