354 
THOMPSON YATES LABORATORIES REPORT 
Description of Figure 
Brain of a Chimpanzee (^Troglodytes niger). Left hemisphere viewed from side and above so as to 
obtain as far as possible the configuration of the sulcus centralis area. The figure involves, nevertheless, 
considerable foreshortening about the top and bottom of sulcus centralis. The extent of the ' motor ' area 
on the free surface of the hemisphere is indicated by the black stippling, which extends back to the sulcus 
centralis. Much of the 'motor ' area is hidden in sulci ; for instance, the area extends into the sulc. cen- 
tralis and the sulc. prccentrales, also into occasional sulci which cross the precentral gyrus. The names 
printed large on the stippled area indicate the main regions of the ' motor ' area ; the names printed 
small outside the brain, indicate broadly by their pointing lines the relative topography of some of the 
chief sub-divisions of the main regions of the ' motor' cortex. But there exists much overlapping of 
the areas and of their sub-divisions which the diagram does not attempt to indicate. 
The shaded regions, marked 'Eyes,' indicate in the frontal and occipital regions respectively the 
portions of cortex which, under faradization, yield conjugate movements of the eyeballs. But it is ques- 
tionable whether these reactions sufficiently resemble those of the ' motor ' area to be included with them. 
The)' are therefore marked in vertical shading instead of stippling as is the ' motor ' area. S.F. = 
superior frontal sulcus. S.Pr. = superior precentral sulcus. I.Pr. = inferior precentral sulcus. 
