DISTRIBUTION OF HEAT. 159 



evaporation of the liquid takes heat from the bulb, and causes 

 the thermometer to register a lower temperature. We sponge 

 the face and hands of a feverish patient to reduce the amount 

 of heat. We sprinkle the floor in hot weather, and, by the 

 absorption of heat in evaporating the water, cool the air of 

 the room. 



When we exercise, we produce more heat ; we sweat more ; 

 more heat is taken from the body to evaporate this greater 

 amount of sweat. If we are not exercising, and are in cooler 

 air, we sweat less, and less heat is given off. 



This should also be observed : When we exercise, more 

 blood is in the skin, and more heat is given off in the other 

 ways mentioned ; when we exercise less, the skin, especially 

 in a cool air, becomes paler, i.e., has less blood in it, and 

 heat is economized. 



Of the total amount of heat given off by the body, eighty- 

 seven hundredths are given off by the skin ; most of the rest 

 is given off by the lungs ; a small amount is given off by the 

 urine, feces, etc. 



Distribution of Heat in the Body. If more heat is 

 produced in one part of the body than in the others, the cir- 

 culation of the blood tends to equalize the temperatures of the 

 different parts. So, too, if one part is cooled, that is, is los- 

 ing heat faster than the others, the blood brings heat from 

 other organs to that part. For instance, if one holds his hands 

 in the snow, or puts a piece of ice on his wrist, the whole blood- 

 stream is cooled. So if the hands and the feet are exposed to 

 the cold, it may do little good to have the rest of the body 

 covered. A pair of wristers and a pair of leggings or gaiters 

 may often add more to one's comfort than a heavy overcoat. 



Regulation of the Production of Heat in the Body. 

 -We have just considered how the temperature of the body 

 may be made uniform by regulating the amount of heat given 



