Dunn, Innervation of the Thigh in tJie Frog. 233 



The amount of this excess is not great, varying in the dif- 

 ferent observations from a minimum of 1 71 fibers to a maxi- 

 mum of 218 fibers. This would include from 6% to 8 % of the 

 number of fibers actually concerned in the innervation of the 

 thigh. But the fact that such an overplus was found in each 

 thigh for each frog calls for some explanation. In the absence 

 of any error this excess can only be accounted for by a branch- 

 ing of nerve fibers and indicates that in each sciatic nerve ap- 

 proximately two hundred fibers have branched. An attempt 

 was made to hit upon some method which would demonstrate 

 the presence of such branching. The process of teasing, which 

 seemed most feasible, was tried and abandoned as unsatisfac- 

 tory, because of the mass of nerve fibers in the sciatic trunk. 

 The separation of the fibers into small bundles and the spread- 

 ing of each bundle in turn under cover-glasses gave better re- 

 sults, but this method was open to the objection that any divid- 

 ing fibers whose branches ran in different bundles would be de- 

 stroyed by the separation. However a number of fibers of large 

 caliber were discovered by this method dividing dichotomously 

 near the point of separation of some one of the sciatic branches. 

 These branching fibers were sufficient in number to render 

 probable the explanation just given. 



4. Proportion of the number of cutaneous to the number of 



muscular fibers. 



The facts ascertained by making a distinction between the 



muscular and the cutaneous fibers are embodied in Tables VI 



and VII. 



TABLE VI. 



T.\bulation of rauicular and cutaneous nerve fibers to the thigh for Frog B. 



