712 Journal of Comparative Neurology and Psychology. 



In the thigh the efferent nerve fibers in the primary branches ont- 

 number the afi'erent fibers, making up more than one-half of the total 

 number of meduUated nerve fibers. In the shank the efferent nerve 

 fibers furnish nearly two-thirds of the entire number of medullated 

 nerve fibers. 



With these corrected numbers, which are of course only approxi- 

 mate, let us see what relation the numbers of efferent nerve fibers 

 for the thigh and the shank bear to the weights of ihe muscles of the 

 respective segments. 



Using the same percentages from the paper of Donaldson and 

 Schoemaker, 1900, as were Used in the discussion of the afferent 

 nerve fibers, we learn that the percentage values for the weights of 

 the muscles of the thigh and shank are respectively 64 per cent and 

 24 per cent of the entire muscle weight for the leg of the frog, and 

 that the ratio is 8 : 3. With the corrected numbers, 895 efferent 

 medullated nerve fibres for the thigh and 541 efferent medullated 

 nerve fibers for the shank, the ratio for the two segments would be 

 895 : 541, or nearly 8 : 5. This more nearly approximates the ratio 

 of the areas of the skin of the two segments than it does the weights 

 of the muscles, the former being 7 : 5. 



We may conclude then that while the afferent medullated nerve 

 fibers are distributed to the segments according to the mass which 

 they innervate, the cutaneous afferent according to the area of the 

 skin of the segment and the muscular afferent according to the weight 

 of the muscle of the segment, the efferent nerve fibers are not distrib- 

 uted according to the mass which tliey innervate, since a greater 

 richness of nerve supply is found in the distal segment, in this 

 instance the shank. While no attempt has been made to correct for 

 splitting nerve fibres, it is possible that, if such a correction could be 

 made, this peripheral richness of pathAvays for efferent impulses 

 would still be maintained. Although splitting increases in the 

 peripheral segment, shown in frog IIB and in the afferent fibers of 

 frog E, it is not so great as to reduce largely the ratio. 



The Innervation of the Foot of the Tegg. 

 We are now at a point where the discussion of the innervation of 

 the foot is possible. From Table III it appears that at the entrance 



