~ 
520 S. WALTER RANSON 
of the axon can be seen and this degenerated stretch extends 
to the cut surface 0.2 mm. distant. As can be seen, there is 
not a, very sharp border between the degenerated portion of 
the axon and the zone of reaction. Isolated portions of the 
reticulum extend into a lightly stained intermediate zone. At 
a, the neurilemma can be seen; at 6, it is stretched over the 
swollen axon and is not differentiated, while at c, both the neu- 
rilemma and myelin sheath can be seen in the preparation but 
were not indicated in the drawing. More rarely one sees two 
dense fibrillar reticula, separated by a zone of light staining 
through which run a few connecting fibrils. 
b. Fibrillar dissociation. In many axons there occurs a sepa- 
ration of the neurofibrils due to accumulation of an excess of 
interfibrillar substance, and at the same time the individual 
fibrils become much more sharply stained. This process occurs 
alike in fibers which have formed a zone of reaction and in those 
which have not. Figure 15 represents a short stretch of an 
axon 0.5 mm. from the cut surface two days after the lesion. 
On following this axon toward the cut surface it is seen to go 
over into a narrow band of fibrils which connect it with a zone 
of reaction near the lesion. Between the part of the axon, 
which was drawn, and the zone of reaction there is a stretch of 
about 0.2 mm. in which most of the axon is fragmented and 
only a narrow band of fibrils connects the two. The accumula- 
tion of interfibrillar substance seems to be more abundant on 
one side of the axon where large spaces are present between the 
fibrils. There does not seem to be any new formation of fibrils 
and only such rearrangement as would naturally take place ~ 
in case of an oedematous swelling of the axon. It will be noticed 
that the network is most dense at the periphery of the axon. 
When this process is carried to its full extent, as one sometimes 
sees it on the second, third and fourth days, the axon becomes 
converted into a fine meshed network forming a hollow cylinder. 
The myelin sheath having disintegrated, this net-like cylinder 
lies immediately beneath the neurilemma. ‘These appearances 
would, of course, be best understood on the hypothesis that 
the fibrils of the normal axon are not isolated but are united 
