130 DR. C. E, BEEVOR AND MR. V. HORSLEY ON THE EXCITATION OP THE 
Results of Excitation— 
A. Cortex, 
B. Internal Capsule. 
Summary and Review of the Character of Localisation in this Animal. 
Anatomy. 
We say nothing here respecting the general anatomy of the animal, having deposited 
the carcass in the Hunterian Museum. 
The area of cortex which we explored comprises the so-called motor region. This 
area is bounded below by the Sylvian fissure, above by the longitudinal fissure, 
posteriorly by the intra-parietal sulcus, and anteriorly by a line drawn vertically 
through about the middle of the three frontal convolutions. It includes the fissure of 
Rolando, the posterior half of the superior frontal sulcus (corresponding to the 
sulcus X in the Bonnet Monkey : vide ‘ Phil. Trans.,’ B, 1887), the prsecentral sulcus, and 
the postcentral sulcus in the parietal lobule (corresponding to sulcus 2 in the Bonnet 
Monkey). Of the two small sulci which are so commonly seen in the Bonnet Monkey and 
in Man at the foot of the ascending or central convolutions, the one which is usually 
situated at the foot of the ascending frontal [v in the Bonnet Monkey'"") was absent, 
while that at the foot of the ascending parietal was not only strongly developed, but 
there was also another small indentation in front of it, in the foot of the gyrus. 
We will now proceed to make a few remarks in detail on these fissures and sulci, as 
we believe that there are certain features in their conformation which are of practical 
importance for the purposes of localisation. 
Fissure of Rolando. 
We have already drawn attention to the shape of this fissure in the Bonnet 
Monkey (‘Phil. Trans.,’ loc. cit.), and we have shown that in that animal it presents 
a well marked genu at the junction of its middle and lower thirds, and we have 
further shown that this genu indicates the lower border of the upper limb area 
of representation. 
In the Orang this genu is extremely well marked, so that in tracing the fissure 
from below upwards it makes almost a right angle as it turns backward, and then, as a 
necessary consequence to reach the upper margin of the hemisphere, it has to turn 
again upwards almost at a right angle, see figs. 1, 2, 3, Plates 16, 17. It follows 
from this that the principal axes of the ascending or central convolutions being 
parallel to the Fissure of Rolando are very flexuous, instead of being merely oblique 
as in the Bonnet Monkey. I'his extreme angularity seems to be a very characteristic 
feature of the anthropoid Apes, as contrasted with the brain of Man, in whom, 
however, it is sometimes seen. 
* See forthcoming paper by the authors on the facial region of representation. 
