Dunn, Medullatcd Nerve Fibers. 705 



nerve fibers to the muscles and 1527 afferent nerve fibers to the 

 skin, making a total of 2301 afferent medullated nerve fibers to the 

 thigh. Table III gives us the number 2059 as the estimated number 

 of afferent medullated nerve fibers innervating the thigh. The 

 excess then is 242 nerve fibers. Such an excess we have interpreted 

 as occasioned by the presence of splitting nerve fibers in the main 

 trunks or in the branches. The percentage excess in this instance is 

 10 per cent. 



Table XII, giving the enumerations in the primary branches of the 

 shank, shows 303 afferent medullated nerve fibers in the branches 

 to the muscles, 1078 medullated nerve fibers in the branches to the 

 skin and 16 fibers in the branches to the joints, a total of 1397 

 afferent medullated nerve fibers to the tissues of the shank. Table 

 III gives us as the estimated number of afferent fibers to the shank, 

 996 afferent medullated nerve fibers, an excess of 401 splitting 

 afferent nerve fibers in the shank, a percentage excess of 28 per cent. 



We may then make the generalization that among the segregated 

 afferent medullated nerve fibers splitting occurs and that it occurs 

 in about the percentage found in the combined afferent and efferent 

 nerve fibers of an intact nervous system. That would imply that 

 splitting occurs among afferent nerve fibers as demonstrated here, 

 and among efferent nerve fibers at approximately the same per- 

 centage, since a like number of splitting nerve fibers must occur 

 among the efferent nerve fibers to maintain the percentage unchanged 

 for the combined afferent and efferent nerve fibers. 



The Distribution of the Muscular Afferent and the 

 Cutaneous Afferent Medullated Nerve Fibers to the 

 Various Segments of the Leg of the Frog. 



We are further justified in making a comparison of the muscular 

 afferent supply with the cutaneous afferent supply in both the thigh 

 and the shank. In the thigh we find that the afferent supply to the 

 muscles is 34 per cent of the entire afferent supply, the remaining 

 Q% per cent innervating the skin. In the shank the muscular afferent 

 fibers make up 22 per cent of the entire afferent supply to the shank, 

 the remaining 78 per cent innervating the skin. Combining the 



