1911.] Motor Localisation in the Brain of the Gibbon. 75 



cells ; their position thus marks the extent of Campbell's precentral or motor 

 area, or of Brodmann's type 4. The extent of the intermediate precentral 

 cortex of the former, or type 6 of the latter, is shown by the smaller dots. 

 The Betz cells are most numerous, largest, and cover a wider zone on the 

 mesial surface of the hemisphere above the sulcus cinguli and on the lateral 



Fig. 3. 



prs., Sulcus precentralis superior, rect., Sulcus rectus, fo., Sulcus fronto-orbitalis. 

 c, Sulcus centralis. 



The black dots in the above figures indicate the area covered by the precentral (motor) 

 and intermediate precentral types of cortex ; the circles the granular frontal type of cortex. 



surface in the neighbourhood of the supero-mesial border (fig. 3). On the 

 lateral surface, below the level of the sulcus precentralis superior (prs.), they 

 are confined to the anterior wall of the sulcus centralis and to a narrow strip 

 of the ascending frontal convolution lying immediately in front of that fissure. 



