TOUCH 213 



cannot feel it because its extremely low coefficient of friction 

 does not allow it to stimulate the touch receptors. 



The receptors for heat and cold are very much fewer 

 than those for touch ; they can be mapped in a similar way 

 by drawing a hot or cold metal point over the surface of 

 the skin. If spots that respond are marked it can be seen 

 that the receptors for heat lie in different places from those 

 for cold, and that both those for heat and cold are separate 

 from those for touch. The temperature-receptors, however, 

 with the exception mentioned below, do not respond to 

 particular temperatures but to relative ones. A heat-receptor 

 is stimulated only by a temperature greater than that of the 

 skin, and a cold-receptor only by one below it. This is easily 

 shown by placing one hand in a bowl of hot water and the 

 other in a bowl of cold, long enough for the temperature 

 of the one hand to be raised and for that of the other to be 

 lowered. If now both hands are put into a bowl of luke- 

 warm water it will feel warm to the cold hand and cool to 

 the warm one. Water of one temperature is thus stimulating 

 the cold-receptors of one hand and the heat-receptors of the 

 other because it is hotter or colder than the skin of the 

 respective hands. 



The receptors for pain are more numerous even than 

 those for touch, probably thereby indicating that they are 

 the most important of the skin receptors. Pain is a very 

 efficient guard for the body in that it prevents animals 

 damaging themselves by contact with objects that might 

 injure them. It is impossible to answer the question so often 

 asked, whether, or to what extent, animals feel pain. Only 

 the animals know that, and we can merely judge by their 

 reactions to stimuli that cause pain to us. By this criterion 

 the answer is that warm-blooded animals, the birds and 

 mammals, undoubtedly do feel pain, though their reactions 

 are often such that we must infer that some of them appear 

 to feel it less acutely than we do. There is no reason for 

 supposing that their receptors are less sensitive than ours, 

 but it may well be that the sensations produced in their 

 brains differ from the equivalent ones in ours. Just as people 

 who coddle themselves become ridiculously sensitive to heat 

 and cold, so it is probable that the softness of civilization 



