Dunn, Medullated Nerve Fibers. 703 



the possibility of the loss of certain efferent nerve fibers also at the 

 entrance level of the leg. Even if frog E has the same length as has 

 frog IIB, it is not probable that it has the same number of medul- 

 lated nerve fibers or the same proportional numbers of afferent and 

 efferent nerve fibers as has frog IIB. Between frogs C and B with 

 the same length a wide variation exists, Dunn, 1900. ISTor can we 

 advance an argument from the proportional numbers of medullated 

 nerve fibers in the ventral and dorsal nerve roots which later inner- 

 vate the leg, because some afferent nerve fibers and possibly some 

 efferent nerve fibers are given off in the pelvis and have not been 

 considered in this enumeration for the branches to the leg. From the 

 size of the nerve branches concerned several hundred nerve fibers 

 might have been so disturbed. 



We are therefore justified in assuming that some loss of efferent 

 nerve fibers has occun-ed in the nerve roots for the right side, and 

 that complete retrograde degeneration is inconsiderable, the retro- 

 grade degeneration being confined chiefly to the periphery. 



The disparity of excess fibers in the two legs of frog E is then 

 due to injury to a few of the efferent nerve fibers of the supposedly 

 intact leg of frog E. Such a change in the medullated nerve fibers 

 might be the result of the somewhat abnormal conditions under 

 which this frog was kept. The possible causes and extent of such 

 a retrograde degeneration from disuse are of great interest, but can- 

 not be taken up at this time. 



Splitting ISTerve Fibers among the Afferent Medullated 

 ISTerve Fibers to the Leg of the Frog. 



Granting that this possible vitiation of the findings for the intact 

 leg of frog E exists, we must consider the value of our counts and 

 the scope of the conclusions which we may draw from them. 



As already established, no vitiation of our findings for the left or 

 operated side is probable. We have then in that leg enumerations 

 at various levels of the complete afferent medullated nerve supply 

 for the leg. In the main trunks those counts for the nerve fibeTs 

 innervating the muscles and those for the nerve fibers innervating the 

 skin are combined, but in the primary branches the muscular and 



