MOTOR CORTEX AND INTERNAL CAPSULE IN AN ORANG-OUTANG. 147 
Face Region. —CombiDation appeared to be universally distributed over the region 
for the face. 
Upper Limb. —Combination was only found in tlie squares for representation of tbe 
small muscles (at squares 83, 28, 29, SO), i.e., at the highest part of the hand region. 
Lower Limb. —Combination occurred most at the squares situated in the vertical 
line drawn towards the middle of the lower limb reafion. 
These facts are simply examples of the principle which we have previously 
enunciated, viz., that the representation of function is most intense on the summits 
of the gyri, and shades off to the sulci, where the excitability becomes nil. 
(B) Internal Capsule. 
We next proceed to raise the upper half of the right hemisphere (after ligature of 
the middle cerebral artery deeply in the Sylvian fissure just in front of the anterior 
limb of that fissure) by a horizontal section carried through the brain, as shown by the 
dotted line in fig. 1, Plate 16, so as to expose the internal capsule. See fig. 5, 
Plate 17. 
Description. —The section exposing the internal capsule of the right hemisphere was a 
horizontal cut jDassing through (from before backwards) the third frontal gyrus, the foot 
of the ascending frontal and parietal gyri respectively, and crossing the posterior limb 
of the Sylvian fissure just where it turns upwards, viz., at about the junction of the 
middle and posterior thirds. The cut surface, viewed from above, exhibited, as is 
shown in the accompanying photograph, fig. 5, taken in the fresh state after the 
excitation, the following points. In front is seen the upper part of the anterior 
commissure, only the middle portion of which appears, as it is soon lost between the 
outer and middle zones of the lenticular nucleus. Posteriorly, in the middle line, the 
splenium of the corpus callosum limits the field of white fibres. Only the two outer¬ 
most zones of the lenticular nucleus are visible, and the caudate nucleus is only 
represented by a small portion of its head separated by a few white fibres from tlie 
putamen or outer zone of the lenticular nucleus. Of the anterior limb of the capsule, 
besides these fibres, there remains only a bundle of fibres about 4 mm. long, running 
directly backwards from the posterior surface of the anterior commissure. The hinder 
limb of the capsule extends from the inner border of the second or middle zone of the 
lenticular nucleus, and on section it is seen that the bundles of transversely cut fibres 
terminate posteriorly opposite the lamina medullaris situated between the zones. 
We mapped out by compasses the cut surfaces of the basal ganglia and capsule, 
upon paper ruled with squares of 1 mm. side, taking care that the posterior limb 
was drawn parallel to the vertical lines of the squares. 
Arbitrary numbers were then applied to each square from which result was 
obtained on excitation, and we now furnish the records of stimulation. 
