1 34 Physiology. 



The Amount of Perspiration. There is about one quart 

 in twenty-four hours. It varies with (i) The temperature 

 and dryness of the air. (2) The condition of the blood, 

 e.g. if watery from drinking much water. (3) Muscular 

 exercise. 



Gland Action and Blood Supply. The sweat glands, like 

 all glands, are largely dependent on the amount of blood 

 supply. In exercising, the skin is usually redder from the 

 greater supply of blood, and at the same time the glands 

 are more active, for during exercise and for some time 

 afterward there is more waste matter to be thrown out. 



Control of the Sweat Glands. But the activity of the 

 gland is not a mere filtering process ; it is not always in 

 proportion to the amount of liquid present. There may 

 be a cold sweat, i.e. when the skin is pale. This usually 

 is due to excitement or emotion, which shows that the 

 action of glands is under the control of the nervous system. 



Sweat Glands are Excretory. The sweat glands rid the 

 body of certain waste matters, and are therefore called 

 excretory glands. A sweat gland is a simple gland. 



Distribution of Sweat Glands. The sweat glands are 

 thickly distributed over the whole surface of the body, but 

 are especially numerous and large on the palms and soles. 

 In the armpits the glands are also large. 



Regulation of tlie Temperature of the Body. It is a very 

 striking fact that, except in disease, the temperature of the 

 body varies only a little from 98.5 F. in winter and 

 summer, during exercise and rest. The rate of producing 

 heat varies greatly. The rate of giving off heat must 

 therefore vary accordingly. 



