CH. XLVIII.] 



LOCALISATION IN MONKEY'S BRAIN 



687 



" solitary cells " ; their axons pass to the oculo-motor nuclei, and so 

 the pathway is provided for the movements of the eyes in accordance 

 with the necessities of vision. 



The marginal convolution on the mesial surface of the hemisphere was first 

 investigated by Schafer and Horsley, in the lower monkeys. They found in these 

 animals that it contained a considerable extension of the " motor" area, including 

 the cortical centres for the trunk muscles. This, at any rate, is not the case for the 

 higher apes, and therefore probably is not true for man. 



Toes 



Ankle \ 

 knee 



Anas 8r,va.gma. 

 ,/' Sulcus 

 ,'.'' . centralis 



Hip 



Abdomen 



.Chest 



Shoulder 

 Elbow 



Wrist 



Fingers 

 5r thumb.. 



Ear 

 fyeltd 



penm 

 of ja.w 



VOCSL! 

 cords 



Sulcus centroJis 



Mastication 



FIG. 498. Brain of Chimpanzee. Left hemisphere viewed from side and above so as obtain the 

 configuration of the Rolandic area. The figure involves some foreshortening about both ends of 

 the sulcus centralis or fissure of Rolando. The extent of the so-called motor area on the free 

 surface of the hemisphere is indicated by black stippling which extends back to the central sulcus. 

 Much of the "motor" area is hidden in sulci ; for instance, it extends into both the central and 

 precentral sulci. The names printed in capitals on the stippled area indicate the main subdivisions 

 of the " motor " area ; the names printed small outside the brain indicate by their pointing lines 

 some of the chief subdivisions of the main areas. But there is much overlapping of the areas which 

 it is not possible to indicate in a diagram of this kind. The shaded regions marked "eyes" in the 

 frontal and occipital regions indicate the areas which under faradisation yield conjugate movements 

 of the eyeballs. They are 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. (After Sherrington and Griinbaum.) 



In experiments on unilateral extirpation in animals, and in 

 destructive lesions of one side of the brain in man, it is the muscles 

 which act normally unilaterally which are most paralysed. The 



