196 BIOLOGY AND HUMAN LIFE 



which was formerly considered a mere accommodation or con- 

 venience, is coming to be recognized as a real necessity. The 

 more progressive cities are also taking steps to provide suitable 

 drinking water for all on the streets and in public places, as 

 well as comfort stations for all who have to be abroad. Under 

 ordinary conditions we give off a quart of water a day from the 

 skin and lungs and about twice as much from the kidneys. In 

 addition to the water that we take as part of our food, and 

 drink with our meals, it is necessary to have access to water 

 between meals ; and in warm weather or at hard work and play 

 the amount must be further increased. 



163. Excretions as health indicators. Our knowledge of the 

 chemistry of metabolism and of the special processes that go 

 on within the body has been increasing rapidly. It is now pos- 

 sible to learn a great deal about the condition of the organism 

 from an examination of the urine, the feces, and the perspira- 

 tion and other fluids or products of the body. The amount of 

 uric acid in the urine, the presence of carbohydrates or of albu- 

 min, bits of cells revealed by the microscope, and so on, all in- 

 dicate distinct facts about what is going on in various parts of 

 the body, not alone in the kidneys; and such information is 

 often of importance to the physician as a means of discover- 

 ing diseased conditions that might not otherwise be suspected. 

 When a person is examined by the physician of a life-insurance 

 company, the urine is included because very often it contains 

 the only sign that the organism is not in good working order. 

 Many lives are being saved by systematically examining the 

 urine and by guiding diet, exercise, etc. accordingly. 



ELIMINATION OF WASTES 



I. Wastes of an organism 



Sources Kinds 



Oxidation of protoplasm Carbon dioxid 



Other chemical processes Water 



Urea 



Other compounds 

 (Oxygen in green plants) 



