NERVES OF THE DOGFISH 391 



nerve trunk, connect some of these ganglia. The most ventral 

 of this group on the main hyomandibular trunk is sometimes 

 much larger than the others (figs. 46 and 47, gsy.). 



After the hyomandibularis has divided into its chief rami, there 

 may be found on the ramus hyoideus three or more of these small 

 sympathetic ganglia. As the ramus hyoideus turns mesially 

 around the lateral border of the hyoid bar to pass between the 

 first and second ventral constrictor muscles, a small branch is 

 given off to the second ventral constrictor. At the base of this 

 nerve branch is a ganglion. Farther mesially, just ventral to the 

 lateral border of the second ventral constrictor, is another gang- 

 lion, this also near the branching of the nerve. A distinct non- 

 medullated nerve runs from this ganglion into the ramus hyoid- 

 eus, and another non-medullated strand, accompanied by one or 

 two medullated fibers runs from the ganglion anterodorsally into 

 the constrictor muscle. Farther mesially still another small 

 ganglion is situated at a branching of the ramus hyoideus, send- 

 ing a non-medullated twig into the muscle. Scattered ganglion 

 cells also are found upon the smaller divisions of the ramus 

 hyoideus (fig. 48). 



On the posttrematic rami of the glossopharyngeus and the 

 first three branchial nerves of the vagus the arrangement is essen- 

 tially as stated previously: two small ganglia on the ramus dor- 

 sally and two ventrally. Figure 48 shows striking variations 

 from this arrangement, but the statement above holds true of 

 most specimens. The ganglia are sometimes little more than 

 scattered cells. Invariably they occur on small branches of 

 mixed constitution. In the fourth branchial nerve of the vagus 

 there are no motor elements, and ganglia are wanting on those 

 portions of the posttrematic ramus passing over the epibranchial 

 and ceratobranchial cartilages. The single elongate ganglion 

 upon the posttrematic ramus is situated at the ventral border 

 of the anterior muscular wall of the esophagus. Its cells are 

 larger and of very different appearance from the cells of the 

 ganglia on the other branchial nerves (fig. 48) . 



