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ward from the lesion in the capsula extrema and capsula externa, but 
mostly in the former, external to the claustrum. A little of this at first 
passes into the superior temporal convolution at a point almost directly 
underneath the lower extremity of the fissure of Rolando (compare Figs. 
16 and 1). A much larger amount, perhaps most of the degeneration 
passing this way, reaches the occipital lobe by way of the optic radiation. 
The remainder of this degeneration, which is very considerable, passes 
around and through the posterior extremity of the lenticular nucleus, 
through the retro-lenticular segment of the internal capsule, and partly 
through the posterior portion of the posterior segment, into and through 
the thalamus, anterior to the pulvinar, to end in the superior colliculus. 
In lower levels a great deal of very fine degeneration running backward 
from the lesion, in the capsula extrema, passes inward, anterior to the 
geniculate bodies, to end in the inferior colliculus; some fibers running 
anterior to the crus pass into the middle third of it and mingle with the 
few degenerated fibers remaining of those which have come down through 
the internal capsule. 
In the sub-thalamie region of the internal capsule the degeneration 
remaining in the posterior segment begins to pass out of the capsule into 
the sub-thalamic region. Many of these fibers pass into or through the 
capsule of the body of Luys; some pass through the centre median— 
some may possibly end in that nucleus—while the most mesial, corre- 
sponding to the most anterior in the posterior segment of the internal 
capsule, leaving the crus in successive levels, pass inward, backward, and 
downward into the central gray matter surrounding the aqueduct. These 
were the last of the degenerated fibers remaining in the crus. 
In CONCLUSION. 
One important question presenting itself on a review of these degenera- 
tions is that of the origin of the mesial segment of the crus—the so-called 
fronto-pontine tract (frontale Briickenbahn, Flechsig). It has been 
very generally believed that the fibers of this tract come from the frontal 
lobe by way of the anterior segment of the internal capsule and end in 
the cells of the mesial pontine nuclei. 
Ferrier and Turner report, following ablation of the frontal lobe in the 
monkey, degeneration in the anterior segment of the internal capsule in 
the most mesial and ventral parts, immediately above the anterior com- 
* Phil. Trans. Royal Soc. of London, 1898. 
