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Relations of the Frontal Lobe in the Monkey 
passing only through the cortex in its upper third. In the middle third 
of the lesion a small portion of the process of corona radiata extending 
into the anterior portion of the frontal lobe was severed from its con- 
nection with the central white mass, while in the lower third the lesion 
was again only cortical. 
In the lower levels of the most anterior portion of the corpus callosum 
a few degenerated fibers crossed the middle line but could not be followed 
to their distribution in the right hemisphere. Most of the degeneration 
passed through the anterior segment of the internal capsule and ended 
in the anterior nucleus of the thalamus. Some degenerated fibers could 
be followed backward through the external capsule, around and through 
the posterior extremity of the lenticular nucleus. In this case these fibers 
could not be traced to their termination, but in the two following experi- 
ments their destination becomes quite clear, and the presence of these 
fibers in this case shows that at least a portion of them take their 
origin from the frontal lobe quite anterior to the lesions in the other 
cases. A small aggregation of degenerated fibers was present in the 
upper levels of the internal capsule, quite above the level of the lesion. 
These fibers could not be traced from the lesion, but that would be 
extremely difficult as the fibers are very fine and probably come in 
singly at different levels. ‘They pass down with the capsular fibers, the 
number increasing from above downward as far as the lowest levels 
of the corpus callosum. In the lower levels of the capsule they are 
confined to the middle third of the posterior segment, from which they 
gradually disappear before reaching the crus. The striations of the len- 
ticular nucleus showed traces of degeneration, more especially in the 
anterior portion of the nucleus. In the middle and lower levels of the 
lesion a few degenerated fibers were found running toward the occipital 
lobe in the optic radiation. There was no degeneration in the anterior 
commissure. No degeneration could be found in the right hemisphere. 
EXPERIMENT B. 
After the removal of the button of bone from the left frontal region 
the knife was passed directly into the substance of the brain, entering 
at a point just anterior to the genu of the pre-central sulcus (Fig. 1, 
L. B.). It was carried inward to a depth estimated to be sufficient to 
reach the middle line, and then downward and slightly blackward to the 
base of the brain with the purpose of cutting off all fibres entering the 
anterior segment of the internal capsule as near as possible to the 
anterior extremity of the lenticular nucleus. The external wound was 
