Va/riations in Spinal Nerves of Hyla aurea. 265 



toward the side of the body for some distance, and turning 

 sharply, often at an angle of almost ninety degrees, runs 

 forwards to supply the muscles of the tongue. In a very few- 

 cases I observed that the hypoglossal divided into two parts 

 which united again a little farther on, leaving a space through 

 which the carotid artery passed towards the head. Between the 

 hypoglossal and pneumogastric nerves there passed in one or 

 two instances a twig of communication which, however, was very 

 tine. Haslam mentions a similar connection as having been 

 described by Hoffmann for Rana* though he himself has not 

 noticed it. The relations of II. with the brachial plexus are 

 varied. Most frequently II. has no connection with the 

 brachial plexus as stated by Adolphi for Bufo variabilis. Some- 

 times a branch passes from II. to join either III. itself, or else 

 the coraco-clavicular branch of III. (cf. Rana esatlen/a, as stated 

 by Weidersheim, Fiirbringer, and Hoffmann), f In a few instances 

 in Hxla aurea, we find that II. is fused with III., and where 

 this is the case, a nerve corresponding in destination to II., and 

 composed also chiefly of IT. fibres, leaves III. to run forwards at 

 the same position as that in which II. ordinarily turns forwards. 

 In one specimen, II., divided into two equal parts at its exit 

 from the intervertebral foramen, the anterior half passing out 

 freely, while the posterior half fused with III. as above, 

 leaving it again to join the anterior part as it turned forwards. 

 According to Ecker j this fusion is not uncommon in Rana. 



III. is the largest of all the spinal nerves. It passes outwards 

 from its origin between vertebra? II. and III., and forms the 

 large Brachial nerve, which supplies the muscles and skin of the 

 arm. While in the trunk, it gives off a branch of considerable 

 size, forming the Coraco-clavlcularls nerve, which supplies the 

 Deltoldeus, Sterno-radlalis, Transverso-scapularis, and Obliquus 

 abdominis Inter mis muscles. As stated above, a branch from II. 

 sometimes joins III. or the coraco-clavicular. Very rarely I 

 found the coraco-clavicular nerve originating from II., with only 

 a small twig from III. Where II. fused with III. entirely, the 

 coraco-clavicular is given off at the same place as II. passes away, 



* Ecker : loc. cit., p. 183. 



t Ecker : loc. cit., p. 183, also Adolphi, loc. cit., 1893, p. 316. 



I Ecker: loc. cit., p. 187. 



