Ranson, F2bers in Lesions of the Brain. 201 
gular area lighter than the rest, representing scar tissue that 
has taken the place of a large blood clot. This runs through 
all the sections, giving, when reconstructed, a mass in the 
shape of a three-sided prism with base directed ventrally. 
Below this lies the corpus callosum degenerated on both sides 
of the lesion. In this case the axons degenerated toward the 
cell whether cut before or after crossing the middle line. <A 
few straggling fibers are seen in the otherwise unstained area. 
These probably represent neurones which have completed their 
development since the operation. 
In the tissue composing the scar numerous nerve fibers 
pass in every direction interlacing to form a large meshed 
irregular network (Fig. 7). Fig. 8 is a camera lucida tracing 
of a part of this same area from another section of this brain. 
Owing to the unusual width of the scar in this region only a 
part of it could be represented in the tracing; the brain tissue 
along its margins is not indicated as in previous tracings. 
The presence of medullated nerve fibers in the cicatricial 
tissue, demonstrated in each of the four brains, might.be ex- 
plained on either of two hypotheses. They might represent 
regenerated portions of nerve fibers cut by the operation ; or 
they might have been formed since the operation by outgrowths 
from cell bodies incompletely developed at that time. Al- 
though there is nothing in the appearance of any given section 
to exclude the former theory, the latter seems the more prob- 
able. This conclusion is supported by the uniformly negative 
results obtained by those who have studied wounds in the brains 
of adult mammals; and by the fact that in the four cases 
given here the number of fibers in the scar diminishes regularly 
as the age of the animal at the time of the operation increases. 
(Compare Fig. 8 with Figs. 6 and 5). These facts might be 
explained as indicating a loss of the regenerative capacity of 
the neurones within the brain as the animal becomes older; but 
are more probably due to the diminution in the number of un- 
developed cells capable of sending axons across the lesion 
subsequently to the injury. During the period of active growth 
with which we have to deal the diminution in the number of 
