702 Jourjial of Comparative Neurology and Psychology. 



place of an expected percentage increase of 5 per cent as in frog IIB, 

 we find a dropping out of nerve fibers so that at the lower level fewer 

 nerve fibers are found than at the upper level. It would appear then 

 that in the right leg of frog E where efferent fibers are present, a 

 peripheral loss of fibers can be absolutely proven. Such a loss of 

 nerve fibers does not appear among the afferent nerve fibers of the 

 left leg. 



Let us see what influence upon the findings for the right leg such 

 degenerating nerve fibers might have. We have previously shown 

 that the loss of nerve fil>ers peripherally would decrease the excess 

 of the observed number of nerve fibers. That excess is 242 nerve 

 fibers for the left thigh of frog E, and 204 nerve fibers for the right 

 thigh. The left thigh contains only afferent nerve fibers, of which 

 242 fibers split. If in the right thigh where efferent nerve fibers are 

 also found, no splitting is found among the efferent nerve fibers, the 

 number of splitting afferent nerve fibers should at least equal the 

 number found among the afferent fibers of the left thigh. At least 

 38 nerve fibers must have dropped out at the lower level which had 

 appeared at the higher level. We have reason, however, to believe 

 that splitting occurs among the efferent nerve fibers as well as among 

 the afferent nerve fibers, so the number lost is probably greater than 

 38 fibers, and just so much greater as it will be when increased by the 

 number of splitting efferent nerve fibers. 



If at successive levels additional nerve fibers have disappeared 

 an explanation is furnished for the greater disparity in the excess 

 for the two shanks than for the two thighs. 



The tabulations for the muscular branches confirm this theory of 

 peripheral efferent loss. Table IV shows 774 afferent nerve fibers 

 for the muscular branches of the left thigh as against 1597 combined 

 nerve fibers for the right thigh, giving a difference of 823 efferent 

 nerve fibers. Table V for the shanks gives 303 afferent nerve fibers 

 in the left shank as against 601 combined nerve fibers in the right 

 shank, a difference of 298 efferent nerve fibers. At the lower level 

 some efferent nerve fibers may have dropped out from the right leg. 



If we accept this argument for the loss at successive lower levels 

 of efferent nerve fibers from the unoperated leg we must consider 



