88 NERVE COMPONENTS OF BONY FISHES. 



The IX root now continues to run directly outward, 

 penetrates the ear capsule and then turns cephalad along 

 the outer surface of the latter, lying ventrally of the vagus 

 ganglion, but not at any time coming into contact with it. 

 Here it is joined by the sympathetic chain, which accom- 

 panies it as far as the IX ganglion and then continues 

 cephalad in the same direction. 



The IX ganglion lies at the point where the nerve turns 

 laterally and ventrally into its gill. A small sympathetic 

 ganglion is applied to its proximal portion. The connec- 

 tion with the sympathetic chain and the anastomosing 

 branch to the root of the r. lateralis vagi are the only con- 

 nections which the glossopharyngeus has with any other 

 nerves. 



2. — Tlie Communis Root of tJie Vagus. 



The vagus proper arises by one great root (640-660),^ 

 which contains three components intimately fused. The 

 great majority of these fibres are communis fibres and 

 pass directly into the lobus vagi, forming the outer fibrous 

 layer of that structure. In this intracranial portion of 

 their course these root fibres separate into two ill-defined 

 tracts, a larger caudal root and a smaller cephalic as shown 

 on Fig. 4. 



Immediately upon entering the oblongata they cross the 

 spinal V tract. This tract, which caudad of this level 

 forms a cord-like protuberance on the dorso-lateral aspect 

 of the oblongata, here breaks up into several large strands 

 and sinks abruptly down to a more ventral position. The 

 root fibres of the vagus interdigitate with these strands so 

 that the relations here are rather confusing. In Fig. 4 

 all of the vagus fibres are conventionally drawn as if they 

 crossed the inner and ventral face of the spinal V tract; 



