EXCRETION. 139 



The Effect of Wet Clothing. In getting the clothing wet, the greater 

 loss of heat is not from the coolness of the water, but the loss of heat 

 in evaporating the water from the clothing. Of course it is desirable to 

 put on dry clothing as soon as possible ; but a person in good health is 

 not likely to take cold, except in very cold weather, if he continues active 

 exercise till he can change the wet garments for dry ones. Children do 

 not often take cold from wading in water so long as they are barefooted ; 

 but if the shoes and stockings are wet, they are likely to take cold. 



Alcohol and Heat. The usual effect of a moderate dose of alcohol 

 is to make the person feel warmer. There is more blood in the skin, 

 where the nerve endings perceive the effect. More heat is brought to 

 the surface and more is given off from the body. A thermometer has 

 no " feelings " by which it can be deluded. The thermometer says that 

 the body is losing heat. It is as though one were to open a window, 

 and as the warm air rushes out by him, were to say, "It is getting 

 warmer," not recognizing the loss of heat. There is some heat pro- 

 duced in the body by the oxidation of the alcohol, but this is over- 

 balanced by the loss as shown by a thermometer. The fact is, as 

 clearly shown by experiment, that alcohol deadens the senses, and 

 neither heat nor cold is so readily perceived as before. And this dead- 

 ening of the senses also makes one fail to notice fatigue ; hence the 

 delusion that the fatigue is gone. 



THE KIDNEYS. 



The Work of the Kidneys. One important part of the 

 work of the lungs, as we have seen, is to throw out carbon 

 dioxid. The skin also throws off certain wastes. The kid- 

 neys have the special task of excreting a waste product of 

 the body called urea. Urea is the nitrogen-containing waste. 



The Parts of the Kidneys. The kidneys are attached to the dorsal 

 wall of the abdominal cavity. The depression in the kidney correspond- 

 ing to the stem scar on a bean is called the hilum. From the hilum 

 issues a white tube, the ureter, which conveys the urine to the bladder. 



The Blood Supply of the Kidneys. Entering the kidney along- 

 side the ureter is the renal artery, a branch of the aorta, and from near 



