PRESSURE AND TEMPERATURE 



2U 



tion. Below is given the weight in grams which could just be 

 detected when placed on various parts of the skin. The values 

 given are normal values (Table XXXIV.). Practice may increase 

 the discriminating point. Every one knows how a blind man 

 " sees " with his fingers. 



TABLE XXXIV. 



Adrian and Zotterman have shown that the electrical discharge 

 in the sensory nerve supplying the toe-pad of a cat varies in fre- 

 quency with the intensity of the pressure applied to the pad and 

 with the rate at which the pressure is increased. The frequency 

 declines when the pressure is kept constant, i.e. adaptation takes 

 place. The rate of decline is not, however, as rapid as in a truly 

 phasic unit, but is more rapid than in a typical postural unit like 

 the muscle-spindle {q.v.). 



5. Temperature. In a similar way one could map out the hot 

 and cold spots and the pain spots in the skin. They vary in 

 distribution, but not in the same order as the pressure spots. For 

 example, the minimum perceptible difference of temperature in 

 degrees Centigrade is given in the succeeding list for various 

 regions (Table XXXV.). 



TABLE XXXV. 



Back 

 Leg 



Thigh 



Back of foot 

 Cheek 

 Temple . 

 Palm of hand 

 Back of hand 

 Arm 



0-9 



0-6-0-2 



0-5 



04 



04 



0-3 



0-3 

 0-2 



10 



