APPLIED PHYSIOLOGY 



the surrounding temperature increases metabolism by 

 2 to 3 per cent. It will be seen from this how expensive 

 a method of regulating temperature increased heat 

 production is. So expensive is it, indeed, that feeble 

 individuals are sometimes unable to produce enough 

 heat, and suffer a lowering of their body temperature 

 in consequence ; and whenever in cases of disease one 

 finds a permanently subnormal temperature, one may 

 conclude that heat production is insufficient. Good 

 examples of such diseases are found in the case of 

 diabetes and myxoedema. 



The heat produced in the muscles in response to an 

 increased demand is distributed throughout the body by 

 the blood, and much of the glow felt after hard exercise 

 is really due not so much to increased heat production 

 as to better heat distribution. If the movement of the 

 blood is languid and the surface bloodvessels contracted, 

 as is the case with persons who suffer from what is called 

 a ' bad circulation,' the heat produced is not well dis- 

 tributed, and consequently such persons have difficulty in 

 maintaining their body temperature when exposed to cold. 



* We are not all blessed,' says Lewes,* ' with the same 

 * The Physiology of Common Life,' i. 436. 



