508 S. WALTER RANSON 
we would assign to the class of afferent spinal non-medullated 
fibers, while the resistant fibers correspond in number to the fibers 
of sympathetic origin. Cajal (08) in one place called attention 
to the slow degeneration of the non-medullated fibers, over- 
looking entirely the much larger number which degenerate very 
early, while in another place in the same monograph he states 
that all the non-medullated fibers have disappeared by the sixth 
or seventh day. 
In Dog v, fourteen days after the operation, the non-medul- 
lated fibers are represented by narrow yellow bands stippled 
with dark brown fine granules. The nuclei are not differen- 
tiated in this preparation. A considerable number of resistant 
non-medullated fibers still retain their intense black uniform 
stain but they present for the most part an irregular contour 
(fig. 6). Some of these fibers seem to. be present after nineteen 
days, but in this specimen new axons have grown in from the 
central stump and might be confused with persistent axons. 
The peripheral stump of the specimen taken twenty-five days 
after the operation is not contaminated with new axons from 
the central stump and here it can be seen that all the old axons 
have degenerated. 
In Dog vy, nineteen days after the operation, the degenerated 
non-medullated fibers are more clearly visible than on the eighth 
and fourteenth day, and the nuclei upon them are well differ- 
entiated. The fibers are fine yellow bands with many nuclei. 
Surrounding many of the nuclei there are considerable accumu- 
lations of protoplasm. A short section of three such fibers is 
represented in figure 7. The fibers are not interrupted as the 
drawing would indicate, but can be followed for considerable 
distances even in relatively thin sections. The fibers andthe 
protoplasm about the nuclei still contain dark brown granules. 
After twenty-five days these fibers present the same picture 
as in the preceding specimen. They are clearly differentiated 
and the nuclei are sharply stained. These fibers are grouped 
in bundles and lie between the protoplasmic bands formed by 
the medullated fibers, from which they can be distinguished 
by their small size and by the absence of myelin droplets. 
