230 Relations of the Frontal Lobe in the Monkey 
rhage within the wound had been greater than in higher levels, but the 
resulting injury was confined to the tissues anterior to the line of incision. 
Throughout the whole extent of the anterior segment of the internal 
capsule the fibers entering it from the frontal lobe had been severed from 
their anterior connections. In the lowest levels the lesion extended only 
about half-way to the middle line, severing the process of corona radiata 
extending to the cortex of the lowest and most anterior portion of the 
Rolandic operculum and to the orbital surface of the inferior frontal con- 
volution from its posterior connections. 
One striking result of this experiment is the insignificant amount of 
degeneration in the severed end of the frontal lobe. There are a few 
fine degenerated fibers running forward from the lesion in most levels 
and there is an occasional fragment of a coarse fiber, but the mass of the 
corona radiata severed from the centrum semi-ovale shows no pathological 
change. In the upper portion of the centrum semi-ovale of the left 
hemisphere, somewhat above the level of the lesion, there is a mass of 
coarse degenerated fibers coming almost entirely from an area of soften- 
ing on the upper surface of the corpus callosum, due to the pressure of a 
small clot. Most of the hemorrhage came from an injured vessel in 
the great longitudinal fissure separating the hemispheres. This mass of 
degenerated callosal fibers was joined in various levels by degenerated 
fibers from the lesion, which could not, of course, thereafter be distin- 
guished from the callosal fibers. After a short course downward a por- 
tion of these fibers was distributed to the cortex of the post-central convo- 
lution in the level of the lower extremity of the inter-parietal sulcus (sul- 
cus retro-centralis inferior) (Fig. 2). The remainder of this degenera- 
tion in the centrum semi-ovale passed downward into the posterior 
segment of the internal capsule, where it was joined by coarse degenerated 
fibers from the lesion in the frontal lobe running backward through the 
anterior segment of the internal capsule. In the upper levels these 
coarse fibers were not grouped in their passage through the anterior seg- 
ment, but below the level of the lower extremity of the fissure of Rolando 
(which is also the lower extremity of the external wound) and just before 
they disappeared from the section and gave place to finer fibers, they were 
confined to the portions of the anterior segment contiguous to the len- 
ticular nucleus, and they mostly reached the posterior segment by breaking 
through the mesial projecting angle of the lenticular nucleus (Figs. 3, 4, 
and 5) quite outside those fibers composing the genu. These frontal 
lobe fibers, together with the remnant of degenerated callosal fibers, form 
a considerable group of scattered degeneration in the anterior half of the 
