706 'Journal of Comparative Neurology and Psychology. 



enumerations for the two segments we find that 26 per cent of the 

 afferent medullated nerve fibers for the thigh and the shank innervate 

 muscles and 74 per cent innervate skin. 



If we confine our attention to the fibers innervating the skin, we 

 may obtain a rough estimate of the relative number of cutaneous 

 pathways for the thigh and the shank, and their relation to the area 

 of skin innervated. In connection with an investigation published 

 by Donaldson, 1903, a series of measurements was made of the 

 cutaneous areas for the thigh, the shank and the foot in the common 

 leopard frog. By those measurements the skin of the thigh was 

 found to be 36 per cent of the total area of the skin of the leg, and 

 the skin of the shank 26 per cent of the entire leg area. The thigh 

 area bore a relation of 36 : 26 to that of the shank, or roughly speak- 

 ing a relation of 7 : 5. 



With 1527 medullated nerve fibers to the skin of the thigh and 

 1094 medullated nerve fibers to the skin of the shank we have a 

 relation of 1527 ; 1094 or again 7 : 5. The distribution of the afferent 

 medullated nerve fibers to the skin of the thigh is then in the same 

 proportion to the area of the skin innervated as is that of the fibers 

 innervating the skin of the shank. So far as we can draw any con- 

 clusions from the frog we find the number of cutaneous pathways in 

 both the thigh and the shank proportional to the area of the skin to 

 be innervated. If then any superior richness of afferent endings 

 occurs in the skin of either of these segments it is due to branching 

 of these primary pathways nearer their terminations in the skin. 



The afferent supply to the muscles of the two segments may be 

 compared in the same way. In the thigh 774 afferent medullated 

 nerve fibers are destined for the muscles, in the shank 303 afferent 

 medullated nerve fibers pass to the muscles. The ratio here is 

 774: 303, or 8: 3. Donaldson and Schoemaker in 1900 ascertained 

 that the percentage values for the weights of the thigh and the shank 

 were respectively 64 and 24 per cent of the entire muscle weight for 

 the leg. The ratio of 64 to 24 when reduced to its lowest terms 

 is 8: 3. 



The distribution of the muscular and of the cutaneous afferent 

 medullated nerve fibers to these two segments is proportional to the 



