CoGHiLL, Cranial Nerves of Aniblystonia. 247 



the ganglion, though there appeared to be no dorsal root of the 

 nerve. 



The second spinal nerve arises by two or more ventral root- 

 lets which fuse into a common root, and by a large dorsal root. 

 The latter arises considerably caudad of the ventral root. In 

 the adult, the dorsal root passes out of the spinal canal through 

 a foramen in the second vertebra. From the foramen it inclines 

 cephalo-ventrad into its ganglion, which is elongated in the 

 same direction. The motor root, emerging from the inter- 

 vertebral space, meets the cephalo-ventral end of the ganglion. 



The ventral ramus {sp. 2 v.) of this nerve is made up of 

 motor and general cutaneous fibers. Its course through the m. 

 intertransversales, to which it sends fibers, is like that of the 

 first spinal nerve. Ventrally of this muscle, it sends fibers to 

 the m. thoraci-scapularis. Proximally of the anastomosis with 

 the second spinal nerve, excepting in the adult, this nerve sends 

 off its entire cutaneous component to the skin of the pectoral 

 region and to the skin anteriorly of this {sp. 2, v, a.). Prox- 

 imally of the anastomosis, also, the main nerve sends fibers to 

 the m. sterno-hyoideus. 



The dorsal rami of the second spinal nerve have a large 

 general cutaneous component. In other respects they do not 

 differ from the dorsal rami of the first spinal. There is, also, a 

 small ramus which extends cephalad into the muscles, which 

 probably corresponds with the first ramus of the first spinal 

 nerve. 



The branchial ramtis of the second spinal nerve arises from 

 the cephalic tip of the ganglion and penetrates the musculature 

 laterad, and emerges in the vicinity of the t. visceralis X. 

 Here it inclines caudad and dorsad, covered by the m. cucul- 

 laris and later by the m. dorsotrachealis. It finally penetrates 

 the latter muscle and divides. One division of the nerve is 

 distributed to the skin of the dorsum. The other division 

 innervates the skin covering the base of the third external 

 gill, and extends into the dorsal portion of this gill as a general 

 cutaneous nerve. It anastomoses in some larvae with a general 

 cutaneous branch of the second t. branchialis vagi. The 



