CEREBRAL LOCALIZATION 



675 



the position and functional character of the motor points in the 1 dog. 

 It is to be noted especially that they are situated on both sides of the 

 crucial sulcus and are sufficiently centralized to' permit, for example, 

 the separate activation of the flexors of the anterior and posterior 

 extremities and other rather specialized movements, such as the re- 

 traction and abduction of the fore limbs, movements of the tail, closure 

 of the eyelids, constriction of the pupils, movements of deglutition, and 

 others. 



The movements themselves are in no way different from those 

 produced in the course of the normal volitional efforts of the animal. 



F " 

 "Eyelid 



&nb*ti* 



Qtening VotAl Mastication, 



of -f&> cords 



FIG. 341. LOCATION OF MOTOR AREAS IN BRAIN OF CHIMPANZEE. 

 The different motor points lie in front of the fissure of Rolando, partly within the 

 sulci. The area marked "eyes" yields conjungate movements of the eyes, but is 

 generally not taken to be a part of the motor area. (Sherrington and Greenbaum.) 



This implies that they are never antagonistic to one another, for the 

 reason that, having evoked a contraction of the flexors, the extensors 

 are momentarily inhibited, and vice versa. This preponderance of 

 one set of muscles, even when the stimulation involves the motor points 

 of both groups, may be destroyed by rendering the nervous structures 

 more irritable by means of strychnin or the toxin of tetanus. Under 

 this condition the cerebral stimulation spreads, activating the entire 

 reciprocal mechanism. We then obtain a strife between the antagonis- 

 tic muscles with the result that the stronger ones predominate. 



As has been emphasized above, the effect of the stimulation of 

 the motor area is unilateral, and is restricted to the side opposite the 

 excitation. There is one exception to this rule and that is conjugate 

 movement. Thus, it will be noted that the stimulation, say of the 



