. The elasmobranch fishes . Fig. 223. Brachial and pelvic plexuses, Eaja vomer. (From Braus.) which runs posteriorly almost to the first dorsal fin. This nerve supplies sense organs of the anterior part of the lateral canal and also pit organs above the line and anterior to the dorsal fin. Many branches are given off from the lateral line nerve as it passes backward in the body to the sense organs along the lateral line canal. The branchial stem in the vagus is a strong bundle which divides into four (pentanchids), five (hexanchids), or six (heptanchids) branchial nerves. The first two or thre
. The elasmobranch fishes . Fig. 223. Brachial and pelvic plexuses, Eaja vomer. (From Braus.) which runs posteriorly almost to the first dorsal fin. This nerve supplies sense organs of the anterior part of the lateral canal and also pit organs above the line and anterior to the dorsal fin. Many branches are given off from the lateral line nerve as it passes backward in the body to the sense organs along the lateral line canal. The branchial stem in the vagus is a strong bundle which divides into four (pentanchids), five (hexanchids), or six (heptanchids) branchial nerves. The first two or three of these branchial nerves, except in Torpedo, where the first and second branchials give off the third and fourth electric nerves, are essen- tially like the branchial division of the glossopharyngeal. Each branchial con- sists of pharyngeal and pre- and post-trematic nerves. The post-trematicus of the vagus is composed of two strong branches, one of which is motor, the other sensory. The motor division innervates the interarcual, interbranchial, adductor, and ventral constrictor muscles. The last branchial nerve is com- posed only of visceral sensory fibers (Norris and Hughes, 1920). The ramus intestinalis or visceralis () proceeds posteriorly after sepa- rating from the branchial stem. Its motor fibers are distributed to the trapezius muscle and to the digestive tract. Its sensory fibers go largely to the digestive tract. The occipitospinales (y, z, fig. 220), back of the vagus, like spinal nerves consist of dorsal and ventral roots, but dorsal roots to the ones most anterior are frequently absent. In lowly forms, as we have seen in Heptanclius, several pairs may be present. As many as five of the ventral occipitospinales have been
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