Dunn, Medullated Nerve Fibers. 



1^7 



that comparison of the nerve fibers of the operated leg with those of 

 the nnoperated leg, by which we might ascertain the relative sizes of 

 the largest afferent and efferent nerve fibers. 



TABLE XVIII. 

 Showing the ratio of the average areas in square micra of the ten largest medullated 

 nerve fibers to the average areas of their axis cylinders at various levels in the 

 operated leg of frog E. 



One result of the pathological condition found in the nerve fibers 

 of the operated leg of frog E is shown in Table XVIII, in which are 

 given measurements in square micra of the cross sections of the 

 entire medullated nerve fibers and their axis cylinders, with the ratios. 

 The ten largest nerve fibers at various levels in the operated leg were 

 selected. The results of the measurements do not correspond with 

 the one to one relation between the axis cylinder and the medullary 

 sheath found by Donaldson and Hoke, 1905. The changes in frog 

 E consist of a slight swelling of the axis cylinder and an associated 

 thinning of the medullary sheath. While the largest average devia- 

 tion found in the normal nerve fiber was 2.3 per cent, the most 

 marked deviation in this frog is 12 per cent. The variation is of 

 significance as showing the effect of abnormal conditions upon the 

 peripheral nervous system without apparent interruption of physio- 

 logical function, and may be due to one or more of the abnormal con- 

 ditions present in frog E. 



Conclusions. 

 After complete degeneration of the medullated nerve fibers passing 

 by the ventral nerve roots to the left leg of a leopard frog, a study 

 of the medullated nerve fibers for both the operated and the intact 

 legs permits the following conclusions. 



