AMPHIBIA. 61 



and skin of the anterior extremity ; those of the dorsal region principally to 

 enter into the structure of the great shell ; some of the lowest dorsal, the 

 sacral, and caudal, are given to the muscles and skin of the posterior 

 extremity, and the generative and contiguous parts. 



10. Fifth cervical nerve. This, with the two next and the first dorsal, form the 



axillary plexus, from which many branches proceed to the large muscles of 

 the shoulder and arm, and the skin ; besides these there are three large 

 nerves, somewhat resembling the median, the spiral, and the circumflex. 



11. Median nerve: it descends and divides into large branches, which pass into 



the substance of the hand, and give branches to the tendinous and muscular 

 parts, and send others towards the skin in the form of digital nerves. 



12. Spiral nerve ; it gives some muscular branches in its course, and passes round 



to the outer side of the arm-bone, and divides and sends a branch through 

 the outer condyle to join another, which is the principal continuation of the 

 nerve, to terminate on the skin at the outer margin and back of the hand. 



13. Circumflex nerve ; it passes upwards beneath that muscle resembling the 



broadest of the back, and gives a branch to the larger teres muscle, and is 

 then directed downwards, to terminate on the skin at the back of the arm. 



14. Ninth dorsal nerve; from this 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 con- 

 nected with the superior part of the pelvis and thigh. 



15. Sciatic nerve ; it is principally formed by the eleventh dorsal and first sacral 



nerves ; it however communicates with the tenth dorsal and second sacral ; 

 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, &c., at the upper surface of the foot. 



