204 



Leyton and Sherrington 



previously noted for right hemisphere in all general features. Left hemi- 

 sphere re-exposed ; motor responses obtained at some points from posterior 





Fig. 26. — Very young chimpanzee ; large lesion in gyrus centralis anterior of left hemisphere. 



strip of centralis anterior not excised ; no motor responses from centralis 

 posterior anywhere, thus agreeing with previous examination. Animal 

 killed by chloroform. 



Ablation-Experiment 7. Removal of part of Inferior Frontal 

 Convolution of Left Hemisphere (fig. 27). 



Troglodytes niger, No. xiv., young adolescent ^, strong, tame. 

 Very vociferous ; subject to fits of anger and excitement, and then becomes 

 very noisy, uttering a considerable variety of sounds, scolding, greeting, 

 petulant, etc. On April 9, after animal had been in laboratory for seven 

 weeks, the skull was trephined under deep anaesthesia, and the lower 

 region of left hemisphere was exposed and stimulated by unipolar faradisa- 

 tion. The post-centralis in the field laid bare, i.e. up to inferior genu, was 

 nowhere found excitable ; pi-ecentralis was excitable continuous throughout 

 its exposed length, i.e. up to genu inferius. The excitable field faded ofi' 

 somewhat gradually in the frontal direction. Certain of the cortical points, 

 the responsive movements of which were specially observed, were topo- 

 graphically recorded as given on the map (fig. 27). A field of cortex in 

 front of the lower end of gyrus precentralis was also mapped (fig. 27) 



