746 CORTICAL MOTOR REGION. [Book hi. 



of particular parts of the fore arm, and that these are arranged 

 in a definite relation to each other. In the more dorsal part of 

 the area, at the base of the triangle, stimulation produces move- 

 ments of the shoulder (Fig. 123); if the electrodes be shifted 

 ventrally movements of the elbow make their appearance; if 

 still more ventrally, movements of the wrist come in, and these 

 are in turn succeeded ventrally by movements of the digits 

 generally, of the forefinger, and lastly of the thumb. A very 

 striking experiment may be made by applying a current of suit- 

 able strength, first at the lower, ventral border of the area, and 

 then gradually advancing upwards towards the mesial line ; the 

 thumb is moved first, then the forefinger, then the rest of the 

 digits, then the wrist, next the elbow, and lastly the shoulder. 

 Further, in certain parts of the area the resulting movement is 

 flexion of the appropriate segment of the limb, in other parts 

 extension, in certain parts abduction, in other parts adduction, 

 and so on. 



Similar exploration shews that the 'area for the hind limb,' 

 lies on the median side of the area for the fore limb, stretching 

 besides on to the mesial surface along the marginal convolution 

 which forms the dorsal portion of the wall of the great longi- 

 tudinal fissure ; it reaches as far back as the intra-parietal sulcus, 

 and is succeeded in front by the 'area for the trunk ' (Fig. 124). 

 Within this general area for the hind limb we may similarly dis- 

 tinguish special areas for the hip (Figs. 123, 124) in the front 

 portion, for the knee and ankle behind this, and for the digits 

 still farther backwards, the area for the great toe being however 

 in front of the area for the other digits. 



In front of the areas for the limbs and trunk, on the median 

 dorsal surface, dipping down into the mesial surface along the 

 marginal convolution (Fig. 124) and reaching laterally on the 

 dorsal lateral surface to the dorsal extremity of the precentral 

 sulcus (Fig. 123), is the ' area for the head,' that is to say for 

 movements of the head brought about by contractions of the 

 muscles of the neck. 



Ventral to this again, in front of the precentral sulcus is the 

 ' area for the eyes,' that is to say, for contractions of the ocular 

 muscles ; and behind the precentral sulcus, ventral to the arm 

 area, lies a small area for movements of the eyelids, brought 

 about by contractions of the orbicularis muscle. Ventral to 

 this again is the 'area for the face,' in which we may distin- 

 guish an area for the mouth, that is an area stimulation of which 

 produces changes in the buccal orifice, opening, shutting, draw- 

 ing to one side &c, and an area for movements of the tongue. 

 These two areas reach downwards to the fissure of Sylvius, and 

 backwards to the line of the intra-parietal sulcus. In front of 

 them, occupying all the ventral part of the precentral convolu- 

 tion and reaching forwards as far as the precentral sulcus, where 



