DEGENERATION AND REGENERATION OF NERVE FIBERS 513 
tion of a distinct neurofibrillar reticulum, and (3) the formation 
of fine fibrils which leave this reticulum and run independently 
through the degenerated myelin. 
The manner of formation of at least some of these inde- 
pendent fibrils is shown in figure 11. In the peripheral part 
of the drawing (p) there is a well-marked neurofibrillar reticu- 
lum from one side of which there arises a lateral branch ending 
in a bulb showing a distinct reticulum. On the central side 
this fiber presents two branches ¢ and c’. It is probable that. 
c’ represents a pre-existing collateral and not a new formed 
branch. Most of the fibrils arising from the central end of 
the reticulum pass into this branch. 
Many, perhaps a majority, of the medullated axons, never 
show any of these changes but undergo an uncomplicated degen- 
eration throughout their entire extent. Those fibers which 
show no reaction near the lesion represent, in all probability, 
the more susceptible fibers, which are well advanced in degen- 
eration throughout their entire extent by the fourth day. The 
more resistant the fiber, the more marked is the reaction near 
the lesion and the more tardy is the fragmentation of the re- 
mainder of the distal stretch. By the eighth day most of the 
products of this reaction have disappeared and by the fourteenth 
day there are no longer any traces of them. 
The changes which have been described in the medullated 
and non-medullated axons of the distal stump are without sig- 
nificance for the ultimate regeneration of the nerve, since all 
the products of this reaction suffer complete degeneration and 
disappear. In themselves, however, these changes are of the 
highest interest. They show that that portion of a fiber which 
is separated from its trophic center does not die at once. It 
continues to live for two or three days and possesses sufficient 
vitality to cause a rearrangement of its fibrils into a complicated 
reticulum and to give rise to lateral branches. The presence 
in reacting medullated fibers of fine fibers budding off from the 
side of a reticulum as shown in figure 11, and the fact that some 
of these fine fibers pierce the neurilemma and run out into the 
endoneurium can only be interpreted as true branching, although 
