The number and size of the nerve fibers innervating the skin and muscles of the thigh in the frog (Rana virescens brachycephala, cope)

1 The innervation of the thigh in the American frog, Rana virescens, shows no marked variation from that of the European frog, Rana esculenta. 2 An enumeration of all the nerve fibers concerned in innervating the hind legs reveals only a slight numerical inequality for the two sides. 3 The nerve fibers concerned in the innervation of the skin and muscles of the thigh are more numerous and of greater average caliber than those innervating the remainder of the leg. Hence in the leg of the frog the fibers of greater diameter run the shorter course. 4 The nerve fibers to the muscles of the thigh surpass both in number and average diameter those which supply the skin of the thigh. 5 From the results of enumeration we conclude that of the fibers which innervate the thigh about 8% divide, one division passing in the main trunk of the sciatic nerve at least to the level S 2 (Fig. II), distal to the last branch of the sciatic nerve. Direct observation reveals some large fibers dividing dichotomously where the branches from the sciatic to the thigh are given off. They are sufficient in number to render the explanation probably correct. 6 The cutaneous nerve fibers of the thigh bear to the cutaneous area which they supply a relation of one fiber to each 1.13‐1.58 square millimeter of this area.