RELATIONS OF THE FRONTAL LOBE IN THE MONKEY. 
BY 
E. LINDON MELLUS. 
From the Anatomical Laboratory of the Johns Hopkins University. 
WITH 20 FIGURES. 
This communication covers the results of three experimental lesions 
upon the frontal lobe in the monkey. The animal employed in experi- 
ment A was the Bonnet monkey (Macacus sinicus), in the other two, 
B and C, the Macacus rheesus. ' The object, in each case, was to sever the 
connection of the anterior segment of the internal capsule with the 
frontal lobe and, by the resulting degeneration, to trace, as far as possible, 
the route and destination of the fibers entering that segment of the in- 
ternal capsule from the frontal lobe. A sub-dural aseptic incision was 
made in each case after the removal of a button of bone. After recovery 
from the anesthetic the animal was carefully watched to observe any 
disturbance of function and killed after the expiration of 10 to 14 days, 
the brain cut in serial sections and subjected to microscopic examination. 
EXPERIMENT A. 
After removal of the button of bone from the left frontal region, the 
knife was passed through the dura directly into the substance of the 
brain in the direction of the median line. The external wound (Fig. 1, 
L. A.), was a perpendicular incision about 6 mm. in length, half-way 
between the pre-central sulcus and the frontal pole, crossed, at the junc- 
tion of the middle with the inferior third, by the fronto-marginal sulcus, 
and at the same time dividing that sulcus into two equal portions. The 
animal recovered quickly from the ether and there was no evidence then 
or at any other time of disturbed function. Fourteen days after the 
operation the animal was killed with chloroform, the brain removed, 
hardened and stained by the Marchi method, and cut in horizontal 
sections. 
Examination of the hardened brain showed the direction of the knife 
to have been inward and slightly downward, reaching little more than 
half-way to the middle line at the point of deepest penetration and 
AMERICAN JOURNAL OF ANATOMY.—VOL. VII. 
