MOTOR CENTRES IN THE MARGINAL CONVOLUTION. 



697 



paralysis nor any deficiency of general or special sensibility.* Excitation of the 

 external surface (motor area) led Ferrier to map out the areas named on p. 695. 

 Schafer and Horsley's experiments agree with Ferrier's, and. t,hey map out the 



Fig. 484. 



The brain with the chief convolutions (after Ecker). See also figs. 498, 499 in their relation to 

 the skull. The numbers 1 to 14, and the letters a to d, indicate cortical areas (p. 696). 

 S, Sylvian fissure ; C, central sulcus, or fissure of Rolando ; A, anterior, and B, posterior 

 central convolutions ; F ls upper, F 2 , middle, and F 3 , lowest frontal convolutions ; f v 

 superior, and / 2 , inferior frontal fissure ; f. A , sulcus prsecentralis ; P l5 superior, P 2 , inferior 



2 1 , gyrus angularis ; ip, sulcus inter- 

 ne, 



parietal lobe, with P 2 , gyrus supra-marginalis ; P, 

 parietalis ; on, end of calloso-marginal fissure ; 

 parieto-occipital fissure ; T 1} T 2 , T 3 , temporo-sphe 

 the coronal suture ; 4j, 4 2 , in the lambdoidal suture. 



lt 2 , 3 , occipital convolutions 



K 2 , K 3 , points in 



motor area into a number of main areas, each of which is particularly concerned 

 with the movement of a particular part or limb, and in some of which, centres con- 

 cerned with more specialised movements may be marked out. The arm-area is 

 roughly triangular (fig. 485), and " occupies most of the upper half of the ascend- 

 ing parietal and ascending frontal gyri, from a little beneath the level of the sagittal 

 part of the precentral fissure below, nearly to the margin of the hemisphere above, 

 together with the adjacent part of the frontal lobe below the small antero-posterior 

 sulcus." It bends round and is continuous with a part of the marginal gyrus. 

 The special movements of the arm are indicated in fig. 485.] 



[The face-area gives rise not only to movements of the facial muscles, but also of 

 the whole of the upper end of the alimentary tube. It comprises the whole of the 



