CEREBRAL CORTEX OF THE HIGHER APES 
353 
though such a fundamental one ; the antero-posterior diameter of the sulcus, being 
an area often five-and-twenty millimetres across, it is, when treated as marking a line 
on the cerebral surface, but a rough guide for any detailed examination of the 
functional topography.] 
Extirpation of the hand area by itself has been followed by severe paresis of the 
hand, the hand being for a few days practically useless and seemingly powerless. In 
a few weeks use and ' power ' were remarkably regained in the hand, so that it was 
once more used for climbing, etc. The animal ultimately not unfrequently fed itself 
with fruit, making use of that hand alone. Even small ablations in the precentral 
gyrus have led to severe though quickly diminishing pareses. On the other hand, 
ablations of even large portions of post-central gyrus have not given any even tran- 
sient paresis. 
III. Other Regions of Cortex 
Our observations indicate that the frontal region, yielding conjugate deviation 
of the eyeballs, presents such marked differences of reaction from the 'motor' area of 
the Rolandic region that we hesitate to include it with the so-called ' motor ' cortex ; 
it seems necessary to distinguish it in a physiological category separate from that. 
Spatially it is wholly separated from the Rolandic ' motor ' area by a field of ' inex- 
citable ' cortex. 
As to the occipital lobe, only from the extreme posterior apex of the lobe and 
from its actual calcarine region has faradization yielded any movement (eyes), and 
then not easily. 
We hope at no long distance of time to be able to lay before the Society a 
detailed account of the completed investigation. Some of our experiments are still 
in progress. 
It is a pleasure to record here our indebtedness to Dr. L. Mond, F.R.S., for 
enabling us to bring these experiments to their present stage. 
