430 THE BODY AT WORK 



when strongly stimulated, yield the same sensation. Indeed, 

 it appears that the mind relies upon the simultaneous stimula- 

 tion of adjacent heat-spots and cold-spots for the assurance 

 that the thing with which the skin is in contact is really hot. 

 If two metal points, one kept warm and the other cold, are 

 applied simultaneously to two closely adjacent spots of skin, 

 the resulting sensation is " hot." When the cold point is 

 withdrawn, or replaced by a second warm point, the sensation 



