DEGENERATION AND REGENERATION OF NERVE FIBERS 599 
In the preceding paragraphs we have recorded the changes 
as they can be observed from day to day in the degenerating 
non-medullated fibers. These observations may be summarized 
and interpreted as follows. The axons of the majority of the 
non-medullated fibers begin to degenerate within twenty-four 
hours after they have been separated from their cells of origin. 
They first become granular and after two or three days become 
broken up into segments of lighter and darker staining. The 
darker stained segments represent the fragmented axon, the 
hghter segments represent accumulations of unstainable sub- 
stance probably of fluid character. It is not easy to determine 
whether the active process is a vacuole formation with exten- 
sion in the long axis of the fiber causing separation of the frag- 
ments of the axon, or whether a retraction of the fragments 
leaves the empty spaces within the neurilemma to be filled with 
exudate. On the fourth day the dark segments have begun to 
disintegrate and by the eighth day the dark segments have 
disappeared, the remains of the degenerated axon are distributed 
as brown granules through the probably fluid contents of the 
neurilemma sheath. During the next stage, eight to fourteen 
days after the operation, the fibers are not very clearly seen. 
But by the nineteenth day the nuclei of the neurilemma have 
increased greatly in number and the fibers again become clearly 
visible, since with the increase in the number of nuclei the pro- 
toplasm has also increased and filled in the old neurilemma 
sheath. We have, therefore, as the terminal stage of the degen- 
eration of the non-medullated fibers nucleated protoplasmic bands 
which differ from the similar bands formed from the medullated 
fibers only in size and in the absence of myelin droplets. 
In this connection certain observations of Perroncito (’09) 
are cf great interest. He noticed that in the neighborhood 
of the bundles of non-medullated fibers spindle shaped cells 
appeared on the third and fourth days and that these became 
more numerous on the seventh and eighth days and lay in con- 
nection with bundles of connective tissue fibers. He failed 
to recognize the formation of the protoplasmic bands from the 
medullated fibers and stated that at last ‘“‘in place of the nerve 
