Dunn, Medullated Nerve Fibers. yog 



ceiitage of splitting among the afferent fibers of frog E, and tliat 

 among the combined fibers for both legs of frog IIB. 



The percentage excess among the afferent fibers for frog E is found 

 in Table IX and is 10 per cent for the thigh and 28 per cent for the 

 shank. The percentage values for frog IIB from Table X show 9 

 per cent for the thigh and 21 per cent for the shank. Both of these 

 sets of percentages are taken from the left leg. 



The percentage excess for the right or unoperated leg of frog E 

 is 66.5 per cent for the thigh and 16 per cent for the shank. This 

 percentage is considerably less than the corresponding excess for 

 frog IIB, 9 per cent for the thigh and 21 per cent for the shank, 

 and still less than the percentage for the operated leg of frog E in 

 which afferent nerve fibers alone appear. 



When w^e compare the percentage excess of the smaller number of 

 medullated afferent nerve fibers found in the left leg of frog E with 

 the percentage excess for the larger number of combined afferent and 

 efferent medullated nerve fibers in the left leg of frog IIB, 2301 

 for frog E and 3481 for frog IIB, if spplitting occurs only among 

 the afferent fibers, the percentage excess for the smaller number in 

 frog E should be considerably greater than for the combined afferent 

 and efferent nerve fibers for frog IIB. This is not the relation 

 observed ; on the contrary the percentage of excess among the com- 

 bined fibers, 9 per cent, is much the same as that for the afferent 

 fibers alone, 10 per cent, therefore we may conclude that among 

 the efferent nerve fibers splitting occurs in about the same percentage 

 as among the afferent medullated nerve fibers. 



The number of fibers dropped out from the right thigh of frog 

 E should be corrected by the addition of the number of splitting 

 fibers to the known loss of 64 nerve fibers. To ascertain the number 

 of splitting fibers we reckon the proper percentage of 823 fibers, the 

 estimated number of efferent medullated nerve fibers in the thigh 

 branches. Ten per cent of 823 is 82. We may conclude that at 

 least the sum of these two sets of nerve fibers, 64 and 82, or 

 146 efferent nerve fibers, has dropped out from the right thigh of 

 frog E. We are not able to say whether these have dropped out from 

 the branches or from the main trunk. 



