55 
OBSERVATIONS ON THE PHYSIOLOGY OF THE 
CEREBRAL CORTEX OF THE ANTHROPOID 
APES 
By A. S. F. GRUNBAUM, M.D., F.R.C.P. 
AND 
C. S. SHERRINGTON, M.A., M.D., F.R.S. 
[Reprinted from the Proc. Roy. Soc, Vol. LXXI] 
SINCE presenting our former note on this subject, we have obtained some further 
observations, though the number is still less than we should wish, owing to the 
rarity and expense of the material. Our further observations have been upon 
five chimpanzees of the commoner variety, and upon one more orang. 
The statements given in our former communication have been confirmed in 
all respects by our observations obtained since then. We can, further, now make the 
following statements in addition : — 
The whole of the surface of the 'island of Red' has proved 'inexcitable' under 
faradization, with currents even considerably more intense than those sufficing to excite 
muscular movements when applied to the precentral convolution. This is noteworthy, 
because the large extent of the insula is a character distinguishing the brain of the 
anthropoid apes from that of the lower apes, and bringing it nearer toward the human 
type. 
Faradization of the cortex of the inferior frontal convolution in either 
hemisphere has failed in our hands so far to elicit movements of any satisfactory 
degree of regularity or constancy ; and this even under use of currents much stronger 
than those which suffice when applied to the ' motor ' cortex proper. The move- 
ments for which, in particular, careful search was made, were those connected with 
vocalization. From the posterior region of the convolution, at scattered points, and 
without constancy even at them, strong faradization occasionally seemed to induce 
movements in the larynx, distinguishable from the rhythmic of respiratory origin. 
Judging from such evidence as we altogether obtained, we conclude that either (i) 
no Broca ' speech centre,' at all distinctly foreshadowing the human, exists in these 
anthropoid brains, or (2) that direct faradization of the Broca speech cortex is 
inefficient itselt to evoke vocalization. These two inferences, are, of course, not 
mutually exclusive, and both the suppositions may be correct. 
