THE SENSE OF TOUCH 



673 



The discriminative sensibility of any portion of the body is a function of 

 > mobility. This is shown by the fact that it increases rapidly from the 

 Loulders to the fingers and from the hips to the toes. 



The Temperature Sense. The sensations of heat and cold which are 



broerienced from time to time are caused by changes in the temperature of 



''he skin produced in a variety of ways. As these sensations are specifically 



ifferent from those of touch, as well as different from each other, it is highly 



robable that for each sensation there are special nerve-endings distributed 



hroughout the skin. Investigations have shown that all over the skin there 



re innumerable spots of varying size which if stimulated evoke sensations of 



heat or cold. Such points are termed heat and cold spots. Each responds 



to but one kind of stimulus. A warm object applied to a heat spot will 



evoke a sensation of warmth. It will have no effect on the cold spot. 1 ne 



reverse is also true. Between the cold and heat spots there are areas that 



are neutral, insensitive to either heat or cold. The cold spots are more 



irJSli 



numerous than the heat spots in almost all regions of the body. (See Fig. 





4-3 



