1036 



CORTICAL MOTOR REGION. 



[BOOK in. 



For instance, stimulation of the more median parts of the gyrus 

 behind the crucial sulcus (Fig. 124 JJ) leads to movements of the 

 hind limb, whereas stimulation of the lateral part or outer end 

 of the same gyrus leads to movements of the fore limb, and we 

 may here distinguish between an area stimulation of which 



FIG. 124. THE AEEAS OF THE CEREBRAL CONVOLUTIONS OF THE DOG, ACCORDING 



TO HlTZIG AND FRITSCH. 



(1) A The area for the muscles of the neck. (2) -f The area for the extension 

 and adduction of the fore limb. (3) 4- The area for the flexion and rotation of the 

 fore limb. (4) JJ The area for the hind limb. Euuning transversely towards and 

 separating (1) and (2) from (3) and (4) is seen the crucial sulcus. (5) Q The facial 

 area. 



(Fig. 124 +) leads to flexion of the fore limb, and an area 

 (Fig. 124 -f) stimulation of which leads to extension of the same 

 limb. In a similar way stimulation of other areas within the 

 ' motor ' region leads to movements of this kind or of that kind of 

 the tail, of the eyes, of the mouth, of other parts of the face, of 

 the tongue, and so on. Obviously in the dog this region of the 

 cortex has connections with the skeletal muscles which do not 

 obtain between other regions of the cortex and those muscles ; 

 and further, the region in question is topographically differentiated, 

 so that certain areas or districts of the region are specially 

 connected with certain skeletal muscles or groups of muscles. We 

 may speak of a ' localisation of function' in this region as compared 

 with other regions of the cortex, and in the several areas within 

 the region as compared with each other. 



The muscles which are thus thrown into contraction are the 

 muscles of the opposite side of the body. When ' the fore limb 

 area,' as we may call it, of the right hemisphere is stimulated, it 

 is the left fore limb which is moved ; and so with the other areas ; 



