206 Prs. A. S. F. Griinbaum and 0. S. Sherrington. 



" Observations on the Physiology of the Cerebral Cortex of some 

 of the Higher Apes." (Preliminary Communication.)- By 

 A. S. F. GRUNBAUM, M.A., M.D. Cantab., M.K.C.P., and C. S. 

 SiiEimxGTON, M.A., M.I)., F.RS., Holt Professor of Physiology, 

 Liverpool. Eeceived July 20, Eead November 21, 1901. 



(From the Thompson Yates Laboratory, University College, Liverpool.) 

 [PLATE 4.] 



AVe have been engaged for some time past on inquiry into the 

 physiology of the cerebral cortex of the anthropoid apes. We are 

 able to lay before the Society some new facts regarding the topo- 

 graphical distribution of function in the anthropoid brain. Our experi- 

 ments have been carried out on individuals representing the four, 

 species Pitliecus satyrus (Orang), Troglodytes gorilla (Gorilla), Troglodytes 

 niger (Chimpanzee), and Troglodytes calv-us (Chimpanzee). The speci- 

 mens so far have included ten adult individuals. Of Troglodytes niger 

 one individual used was only a few months old. 



I. Method employed. 



The method of excitation employed for the cortex has been unipolar 

 faradisation, in the manner previously adoped by one of us* in examining 

 the cortex cerebri for ocular reactions. This method allows of finer 

 localisation than that possible with the double-point electrodes ordi- 

 narily used. The inductorium (Kronecker's pattern and scale) has been 

 Helmholtzed. 



II. " Motor " (so-called} Area. 



This area we find to include continuously the whole length of the 

 precentral convolution. It also enters into the whole length of the 

 sukus centmlis, with the usual exception of its extreme lower tip and its 

 extreme upper tip. 



In all the animals examined, we have found the " motor " area not 

 to at any point extend behind sulcus centralis. Feeble reactions can 

 occasionally, under certain circumstances, be provoked by strong 

 faradisation behind the sulcus cent rail*, but these are equivocal, and 

 appear under conditions that exclude their acceptance as equivalent to 

 " motor-area " reactions. 



On the mesial surface of the hemisphere the " motor " area has 

 extended less far down than was expected. It has riot extended to 

 the calloso-marginal fissure. Certain areas near that fissure have 

 yielded us movements, e.g., of shoulder, body, wrist, and fingers ; but 



* Sherrington, ' Boy. Soc. Proc.,' vol. 52, 1893. 



