THERMAL SENSATIONS 



457 



These functions E and / seem to resemble exponen- 

 tial functions with different constants as follows: 



When the temperature 6 = 6,,, n = o. l( a < l3, 

 we obtain curves as shown in figure 26 where the 

 difference curve, n, resembles the experimental curves 

 of the steady discharge obtained from single cold 

 fibers. 



In the above equation only the temperature de- 

 pendence has been considered. The time dependence 

 can, however, be included in the equation in a manner 



which rather closely describes the "adaptive' part of 

 the response of thermal receptors, i.e. the response to 

 sudden temperature changes. The equation can be 



written: 



n = A[(a, - e--")£ - (6, - e"'^')/]- 



The constants are dependent upon the previous 

 excitatory level of the thermal receptor. Figure 26 

 shows how these functions can be used to predict the 

 behavior of a cold receptor at a sudden drop in tem- 

 perature from di to d-i and back again. For further 

 details and the computation of the constants see 

 Hensel (45). 



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