138 PHYSIOLOGY. 



body to evaporate this sweat. If we are not exercising, 

 and are in cooler air, we sweat less, and less heat is given 

 off. So the temperature of the body is kept uniform. 



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. 



Distribution of Heat in the Body. If more heat is 

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

 circulation of the blood tends to equalize the temperatures 

 of the different parts. So, too, if one part is cooled, 

 that is, is losing 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 

 affected. 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 may 

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



Regulation of Bodily Temperature by Food and 

 Clothing. When subject to the influence of cold we eat 

 more ; we choose more heat-producing foods, as fatty food- 

 stuffs ; we take more vigorous exercise ; we put on more 

 clothing, and especially of the non-conducting kinds, 

 woolens. In warmer weather we eat less fatty matter, 

 wear less clothing, and are less disposed to exercise 

 actively ; we fan ourselves to help get rid of heat ; we 

 take ices and cold drinks. For most persons it seems 

 better to wear woolen most of the time, as even in summer 

 we are subject to sudden changes in the air, and with such 

 covering one is less likely to take cold. 



