HOW THE BODY LOSES HEAT 



221 



chapters. A certain amount of heat is lost by conduc- 

 tion, although the air is a very poor conductor, and warm 

 fabrics get much of their heat-holding qualities because of 

 the stagnant air confined in their meshes. Most of our 

 heat from the body is lost by convection. When we 

 fan ourselves, we create a current of air, causing cooler air 

 to replace the 

 warm air about 

 the body. We 

 also lose heat 

 by radiation to 

 other solid ob- 

 jects which are 

 cold. It is very 

 easy to take cold 

 by sitting on the 

 damp ground, or 



close to cold 

 windows or 

 walls, because in 

 this way warmth 

 is removed rap- 

 idly from one 

 part of the body. 



Which side of this boy will lose more heat ? Why ? 



Curiously enough, although we feel warm when we per- 

 spire, yet much of the heat of the body is taken away 

 by evaporation of the water from the body surface. On 

 a hot muggy day when the atmosphere about us is moist, 

 little heat is lost by evaporation and we feel much hotter 

 than on an equally hot dry day when we perspire freely. 

 A person may feel the heat far more in New York on 

 a day in August than in the jungles of British Guiana at 



