624 



THE HUMAN BODY. 



for the areas marked leg, foot, and face, except that the re- 

 sulting degeneration would extend in the one case to the 

 lumbar enlargement of the cord, in the other to the nucleus 

 of the vn nerve in the medulla. Moreover, each of these 

 areas can be mapped out into smaller ones, giving origin 

 to a more limited movement when stimulated and a more 

 limited paralysis and tract of degeneration when removed. 

 Thus areas especially associated with the eyelids, with the 

 muscles of the angle of the mouth, with the flexor muscles of 



Pa 



Fv 



FIG. 179. Diagram of outer surface of left cerebral hemisphere to illustrate the 

 localization of functions. The motor area is shaded in vertical and transverse 

 lines: .Vj/, fissure of Sylvius; an, angular gyrus or convolution; Ro, fissure of 

 Rolando; Fv, frontal lobe; Pa, parietal lobe; Te, temporal lobe. Only a very few 

 of the more important fissures are indicated. Compare with Fig. 180. 



the wrist, all have their definite places in the general face or 

 arm region. So definite are the positions of these areas that 

 in cases of localized paralysis, diagnosed as due to lesions of 

 the cerebral cortex, surgeons now have no hesitation in open- 

 ing the skull in order if possible to remove the cause of 

 trouble, as a small tumor: they know precisely in what spot 

 they will find it. Although the localization is therefore 

 tolerably precise, yet the limits of neighboring areas are not 

 as sharp cut as the boundaries of neighboring countries on a 

 map: as shown in Fig. 179, the arm area in its lower part 

 overlaps part of the face area; and the minor areas within 

 the main ones also overlap one another at their margins. 



The general interpretation put upon the above facts, and 

 one which seems justified, is that in making definitely willed 



