Dunn, Nerve Fibers of the Fjvg. 305 



or a certain cutaneous region, irrespective of its method or 

 point of separation. 



The differences in the innervation of the shank between 

 Rana virescens and Rana esculenta are in detail as follows. 



The branch designated in Figures i and 2 and Table II as 

 T/3 which in Rana esculenta is given off directly from the tibial 

 nerve, in Rana virescens is given off with Ta , the ramus cutaneus 

 cruris posterior. This branch T/i is one of the branches inner- 

 vating the M. plantaris longus. A similar joining of a mus- 

 cular and a cutaneous branch is found in the thigh in the 

 instance o{ S 2 and S ^ which in Rana virescens are frequently 

 given off together. 



2. One branch to the M. tibialis anticus longus is given off 

 from the main trunk of the N. peroneus in addition to those 

 branches arising from the N. peroneus lateralis and the N. 

 peroneus medialis. In Rana esculenta all the fibers supplying 

 the M. tibialis anticus longus pass by way of the N. peroneus 

 lateralis or the N.' peroneus medialis. 



Section II. Number and Diameter of the Nerve Fibers In- 

 nervating the Thigh, Shank and Foot. 



A. Int7'odnction. 



The results obtained from a series of observations under- 

 taken to ascertain the number and diameter of the fibers in- 

 nervating the thigh made probable the deduction that, contrary 

 to the long accepted statement of Schwalbe, 1882, the largest 

 nerve fibers do not run the longest course and so innervate the 

 foot, but pass at a comparatively high level to innervate the 

 tissues of the thigh. 



This deduction rests upon two ascertained facts. The first 

 is that the average area for the nerve fibers at the level just 

 above the thigh branches, S^ Figure 2, is greater than that for 

 the fibers at a level just below the thigh branches, S, Figure 2, 

 and is less than the average area for the fibers of the thigh 

 branches. The second fact is that by actual measurements of 

 the ten largest fibers in each of these three regions it was ascer- 

 tained that the very large fibers that are present above the 



