CRANIAL NERVES OF CAECILIANS 547 



In Ichthyophis the origin and course of the occipital nerve 

 are much as in Herpele (fig. 35) but it nowhere comes in contact 

 with the vague root ganghon. In Geotrypetes, Dermophis and 

 Caeciha (figs. 37, 36) the occipital nerve contributes an important 

 element to the hypoglossal nerve. 



In the occipital nerve we see represented a ventral division 

 of a spinal nerve. It possesses two parts: a ventral branch to 

 the hypaxonic musculature, with sometimes a more specialized 

 contribution to the hypoglossal area, and a dorsal branch to the 

 dorsal trunk musculature. Of the forms studied, only in Her- 

 pele does the occipital pass through the vagus ganglion. We 

 may therefore infer that there is no anastomosis between the 

 occipital and the vagus in any caecilian. 



THE FIRST SPINAL NERVE 



This nerve arises from the central nervous system in a manner 

 similar to the preceding nerve, and passes out through a canal 

 in the first vertebra, the characteristic exit of the first spinal 

 nerve in Amphibia. Soon after emerging it divides into dorsal 

 and ventral divisions, (fig. 34, sp.l) the former of which goes to 

 the dorsal trunk muscles, and the latter, after sending off a small 

 branch to the rectus subvertebralis muscle, passes posteriorly 

 and laterally in the interval between the lateral and medial 

 portions of this muscle (fig. 38) , and approaches the main trunks 

 of the sympathetic and vagus nerves, parallel to which it runs 

 for some distance. Then it gradually passes, dorsal to the sym- 

 pathetic, around to the lateral border of the second sympathetic 

 ganglion (fig. 39), a short distance posterior to which it fuses 

 with a cutaneous branch of the second spinal nerve (fig. 40, 

 sp.l + sp.2) which has already passed through the sympathetic 

 ganglion. The nerve trunk thus formed turns ventrally and 

 anteriorly in the space between the levator arcuum branchialium 

 muscle and the extreme anterior end of the lateral division of the 

 rectus abdominis muscle, grazing the lateral border of the ramus 

 intestino-accessorius X, as the latter curves ventrally from its 

 anterior dorsal position (fig. 40). This trunk, formed by these 



