CHAPTER VI 

 FUNCTIONS OF THE KIDNEY 



All the waste matter of digestion and of bodily activ- 

 ity is not carried away in the feces. Some elimination, 

 particularly of water, takes place through the lungs, 

 some through the skin, but the major part through the 

 kidneys. The product of the activity of this pair of or- 

 gans is the urine. 



Urine, in man, is a more or less straw-colored fluid, the 

 color varying greatly even in health and still more in 

 disease, from an almost colorless liquid to a dusky red. 

 Urine, in health, shows a slightly acid reaction, i.e., 

 turns blue litmus paper red, due to the presence of salts, 

 chiefly sodium, so combined as to form acid phosphates. 

 This activity is increased on an animal diet and dimin- 

 ished on a vegetable diet, sometimes even disappearing 

 so that the urine is neutral, has no action on litmus pa- 

 per or even turns red litmus blue; the urine becomes 

 alkaline in reaction. The average specific gravity of 

 urine is 1.020. The amount passed in a day is from two to 

 three pints but varies under so many conditions, even 

 in health, that a specific amount can not be stated. In 

 general the statement may be made that the amount of 

 urine varies more from the activity of the skin than 

 from any other single condition. Thus, in warm 

 weather, when one perspires freely, the amount of urine 

 will decrease and the color will be high. Exercise, or 

 any other condition, which increases the formation of 

 sweat, will decrease the amount of urine. A cold bath 

 or a sudden change of weather to a lower temperature, 



82 



