5 o6 TEXT-BOOK OF PHYSIOLOGY. 



The Motor Area. The general motor area is represented as 

 occupying the pre-central convolution, the base of the first convolu- 

 tion, both on its lateral and mesial aspects, and the paracentral lobule. 

 The exclusion of the post-central convolution from the motor area 

 is in accordance with the embryologic researches of Flechsig, which 

 indicate that the efferent fibers which compose the pyramidal tract 

 come from the region anterior to the central fissure, and with the 

 experiments of Sherrington and Grunbaum on the brain of the chim- 

 panzee, which demonstrate that the post-central convolution is 

 absolutely inexcitable to electric stimulation. It is quite probable 

 that with the growth of the brain in size and complexity, the motor 



CONCRETE CONCEPT 



FIG. 226. THE AREAS AND CENTERS OF THE LATERAL ASPECT OF THE 

 HUMAN HEMI-CEREBRUM. (C. K. Mills.') 



area has come to occupy a position somewhat farther forward in the 

 human brain than in the monkey brain. 



This general area is also capable of subdivision into areas of 

 variable size, in which the movements of the face and associated 

 structures, the head and eyes, the arm, trunk, and leg, are represented. 

 The sequence of their representation from below upward is similar 

 to that observed in the monkey and chimpanzee. A localized irritative 

 lesion of any one of these areas gives rise to convulsive movements of 

 the muscles of the opposite side of the body, similar in character to 

 those resulting from electric stimulation of the corresponding areas of 

 the monkey and ape brains. Destruction of these areas from the 



