54 APPLIED PHYSIOLOGY 



Of these, the skin alone is utilized for purposes of 

 regulating the temperature in man. 

 Heat is lost from the skin 



1. By radiation. 



2. By conduction. 



3. By convection. 



4. By evaporation. 



1. Radiation is by far the most important of these, 

 for 73 per cent, of the total loss from the skin, or 

 1,700 Calories, may be accounted for in this way. 

 Eadiation is most active in cold, dry air, and the 

 greater the surface of the body relative to its mass, the 

 greater is the loss by radiation. Small animals, there- 

 fore, tend to lose heat more rapidly than large, which is 

 the chief reason why children should be warmly clothed. 

 It would appear that the amount of heat lost by radiation 

 cannot be varied much by natural means, for even such 

 a degree of dilatation of the surface capillaries as will 

 produce visible redness only serves to raise the surface 

 temperature of the skin 1*75 C. (Hale White). 



2. Conduction. Seeing that water is twenty-eight 

 times better as a conductor of heat than air, it will be 

 obvious that the greater the degree of moisture in the 

 atmosphere, the greater is the loss by this means; 

 hence the chilling effect of cold, damp air. Fortunately, 

 however, the human body is a bad conductor of heat. 

 Indeed, it may be compared to a mass of but moderate 

 conducting power containing a warm substance the 

 blood of almost constant temperature, and the tem- 

 perature of any point in the body depends upon its 



