EXCRETION. 1 39 



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 ; and this goes on for a long time. 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 shops and stock- 

 ings are wet, they are likely to take cold. 



Sunshine. For good health we need sunshine. We 

 have sunlight indoors, but so do many plants that drag 

 out a sickly existence. We need direct sunlight (not too 

 hot), and many an invalid has been cured by sunbaths. 

 Part of the beneficial effects of sea bathing is due to sun- 

 shine. It is a good thing that it is now the fashion to take 

 a vacation and become well tanned. One of the benefits of 

 the resorts of Colorado (in addition to the climate's mild- 

 ness) is that there are very few cloudy days during the year. 



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 Kidney. 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 



