SKIN SENSATIONS. 



193 



being more numerous, are more sharply defined than those of 

 warmth; the latter are also much more readily fatigued. This 

 fact must be remembered in repeating the observations. 

 More intense heat stimuli, besides stimulating the warm spots, 



also stimulate those of jgold causing a cold sensatio 



Experiment 80. 



Test this using a temperature of about 50 C, 

 Mechanical and electrical stimuli, etc., applied to hot and cold 

 spots, may call forth thermic sensations. 



Experiment 81. Select a few pronounced cold and hot spots. 

 and stimulate them by tapping lightly with a small round 

 pointed object, or by applying the tetanizing electric current. 



IP 



FIG. 59. Heat and cold spots on the skin of the palm of the left hand: (a) 

 heatspots; (b) cold spots. The depth of the shading in each case represents the 

 intensity of the sensation. 



The sensation of temperature remains for some time after the 

 condition causing it has been removed (temperature after-sensa- 

 tions). 

 Experiment 82. Place on the forehead a coin which has been 



either cooled or warmed, and note the nature of the sensations 



which are experienced after its removal. 



The temperature sense is not equally acute over the body. 

 Many factors influence the acuity but in general it may be stated 

 that clothed parts are more sensitive than unclothed, with the 



