GENERAL SENSATIONS 399 



PAIN 



Threshold Value. Arrange an inductorium for 

 tetanizing currents. Place the electrodes on 

 the tip of the tongue, and move the secondary 

 toward the primary coil until no farther move- 

 ment can be made without causing the stimula- 

 tion to become painful. Determine for this 

 region and for others of the mucous membrane 

 of the mouth and of the skin what distance of 

 the secondary coil from the primary separates the 

 stimulus at which pain is just perceived from 

 that at which the pain is distinct. 



Latent Period. In several individuals measure 

 approximately the interval between the applica- 

 tion of the stimulus (single break shock) and the 

 resulting painful sensation. 



Summation. Determine the number of sub- 

 minimal stimuli necessary to produce pain. 



Topography. Map upon the skin of the face 

 and arm the areas specially sensitive to pain. 



Individual Variation. Compare the reactions 

 of several individuals, and note the differences in 

 threshold value, latent period, summation, and 

 topography. 



Temperature Stimuli. Fill two bowls or large 

 beakers with water twenty-five degrees respec- 

 tively, hotter arid colder, than the temperature 



