DEGENERATION AND REGENERATION OF NERVE FIBERS 517 
distance from the cut surface. From this point to a point at 
a distance of 10 mm. from the lesion the intensity of the degen- 
eration decreases until at 10 mm. there are exhibited changes 
similar to those seen at the end of the second day in the distal 
stump. There are here the same breaking up of the fibers 
into light and dark segments and the same granular staining 
as has already been described in the distal stump. In the proxi- 
mal stump, however, there is the important difference that the 
intensity of the process decreases rapidly in a central direction; 
and although our section, only a little more than 1 em. in length, 
does not permit us to say at just what point the degeneration 
ceases, there can be little doubt that it does not extend more 
than 2 cm. up the nerve. We are dealing here with a celluli- 
petal or retrograde degeneration. 
A. slow, ascending, cellulipetal, or retrograde degeneration 
has been noted in the medullated fibers in cases of long stand- 
ing amputation (Ranson ’06). It is questionable whether such 
a degeneration occurs in any of the medullated fibers within 
the time covered by this series of experiments; no clear evidence 
of its occurrence could be found after thirty-four or thirty-five 
days. Its occurrence in the non-medullated fibers is of special 
interest since it indicates a greater susceptibility of the neu- 
rones, of which they form a part, to lesions of the peripheral 
nerve. On cutting the dorsal ramus of the second cervical 
nerve in the white rat, near the ganglion, Ranson (’06) noted 
that 52 per cent of the cells in the associated ganglion under- 
went complete degeneration. It was later shown (Ranson ’09) 
that the cells which disappeared were the small cells, which we 
now know to be associated with the non-medullated fibers; 
while very few, if any, of the large cells, which are associated 
with the medullated fibers, disappeared. 
While in those experiments the cut was made very close to 
the ganglion, in the present series of experiments the sciatic 
was divided at a relatively great distance from the ganglion. 
And, following the law that the intensity of the reaction in 
the cell depends upon the proximity of the lesion in the axon 
to the cell-body, the division of the non-medullated fibers 
