454 TEXT-BOOK OF PHYSIOLOGY 



largely vegetable in character and rich in alkaline salts, is either neutral or 

 alkaline in reaction. The diminished acidity after meals is attributed to the 

 formation of hydrochloric acid by the gastric glands and the consequent 

 liberation of bases which are excreted in the urine. The phosphoric acid 

 which enters into combination with sodium and potassium bases is a product 

 of tissue metabolism. 



The specific gravity is about 1.020, though it varies from 1.015 to 1.025. 

 It will diminish, other things being equal, with increased consumption of 

 water and diminished activity of the skin; it will be increased of course by 

 the opposite conditions. 



The quantity of urine excreted in twenty-four hours varies from 1200 to 

 1700 c.c. Amounts both above and below these are frequently passed from 

 a variety of causes. 



Chemic Composition. The chemic composition of the urine is very 

 complex and is determined partly by the metabolism of the constituents of 

 the tissues and partly by the quantity and the quality of the food consumed 

 and metabolized. Hence the composition will vary from day to day in 

 accordance with the character of the food. An average composition is 

 presented in the following table: 



THE CHEMIC COMPOSITION OF URINE 



Water 1500.00 c.c. 



Total solids 72 .00 grams. 



Urea 33 . 18 grams. 



Uric acid (urates) 0.55 grams. 



Hippuric acid (hippurates) 0.40 grams. 



Kreatinin, xanthin, hypoxanthin, guanin, ammonium \ arum* 



salts, pigment, etc J 



Inorganic salts; sodium and potassium sulphates, phos- 

 phates, and chlorids; magnesium and calcium phos- 



phates. 



27.00 grams. 



Organic salts: lactates, acetates, formates in small 



amounts 



Sugar a trace 



Gases, nitrogen, and carbonic acid. 



The Total Solids. It is frequently a matter of clinic interest to deter- 

 mine the total amount of the solid constituents excreted in twenty-four hours. 

 This may be attained approximately by multiplying the last two figures of 

 the specific gravity by the coefficient 2.33 of Haeser or Christison. The 

 coefficient of Jones, 2.6, is believed by some observers to give more accurate 

 results for conditions existing in this country. The result expresses the total 

 solids in 1000 parts :'e.g., urine with a specific gravity of 1.020 would contain 

 20 X 2.33, or 46.60 grams of solid matter per 1000 c.c. If the amount 

 passed in twenty-four hours be 1500 c.c., the total solids would amount to 

 69.9 grams daily. 



The Water of the Urine. The amount of urinary water and its ratio 

 to the solid constituents will vary with the amount consumed and the activity 

 of the skin and lungs. In summer the foods, liquid and solid, remaining the 

 same, the quantity of water in the urine is diminished in consequence of 

 increased activity of skin and lungs and the ratio of water to solids decreased. 

 In winter the reverse conditions obtain. The food remaining the same, the 

 consumption of large quantities of water hastens at least the removal of end- 

 products from the tissues and thus increases the urinarv solids. 



