AMPHIBIA. 41 



nerve and the tenth, the nerves representing the anterior crural, obturator, and other 

 nerves usually proceeding from the lumbar, are given off; these are distributed on the 

 muscles and skin connected with the superior part of the pelvis and thigh. The 

 sciatic nerve is principally formed by the eleventh dorsal and first sacral nerves ; it 

 divides into two principal parts, one of which gives branches to the muscles of the 

 thigh, and is continued on the under surface of the foot, and terminates on the skin, 

 like digital nerves ; the other, after giving off some muscular branches, passes to the 

 skin and other structures on the upper surface of the foot. In the snake, the spinal 

 cord begins at the termination of the oblong medulla ; it is continued quite to the 

 end of the tail ; it is of nearly the same size throughout to this part, and then becomes 

 gradually smaller ; it has cineritious matter within it. It gives off anterior and 

 posterior bundles of nerves ; their roots are very close to each other, and the anterior 

 is rather larger than the posterior ; at the anterior point the anterior bundle becomes 

 connected with it ; after this union, it sends a posterior branch backwards to the 

 muscles and skin ; the anterior proceeds forward to some distance between two ribs, 

 and sends branches between them to the exterior of the body, and then is continued 

 over the inner surface of the anterior portion of two ribs, to terminate on the anterior 

 part of the body. In the frog there is one large nerve, instead of the axillary plexus. 

 The nerves of the cauda equina terminate in the anterior crural and sciatic for the 

 lower extremity. 



SYMPATHETIC NERVE. In the turtle, testudo mydas, the sympathetic is 

 very closely connected with the par vagum, but in the testudo imbricata it is more 

 separate. There is not any appearance of a superior cervical ganglion : from the 

 upper part of the trunk one branch passes forwards along with one of the divisions of 

 the carotid artery, in a canal at the base of the skull, gives a filament to the hard 

 portion of the seventh, and communicates with a branch of the second trunk of the 

 fifth, which terminates on the posterior part of the palate. Another branch passes 

 with the other division of the carotid artery into the reticular sinus, close to the 

 external auditory meatus, and communicates with the ninth, par vagum, glosso- 

 pharyngeal, and the hard portion of the seventh. It passes down, in connexion with 



G 



