EXCRETION. 471 



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

 a variety of causes. 



The odor of the urine is characteristic and due to the presence of aromatic 

 compounds. 



COMPOSITION OF URINE. 



Water 1500.00 c.c. 



Total solids 72 .00 grams. 



Urea 33 .18 grams. 



Uric acid (urates) o . 55 grams. 



Hippuric acid (hippurates) o .40 grams. 



Kreatinin, xanthin, hypoxanthin, guanin, ammonium 



salts, pigment, etc. 

 Inorganic salts; sodium and potassium sulphates, phos- 

 phates, and chlorids; magnesium and calcium phos- 

 phates. 



ii .21 grams. 



27.00 grams. 



Organic salts: lactates, acetates, formates in small 



amounts 



Sugar a trace 



Gases, nitrogen, and carbonic acid. 



The estimation of total urinary solids in any given sample of urine is 

 frequently a matter of clinical interest. This may approximately be attained 

 by multiplying the last two figures of the specific gravity by the coefficient 

 of Haeser or Christison, 2.33. The result expresses the total solids in 1000 

 parts: e.g., urine with a specific gravity of 1.020 would contain 20X2.33, 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 urinary solids. 



Urea. Urea is the most abundant of the organic constituents of the 

 urine and is present to the extent of from 2 to 3 per cent. It is a colorless 

 neutral substance, crystallizing under varying conditions hi long silky needles 

 or in rhombic prisms. It is soluble in water and alcohol. It is composed of 

 CON 2 H 4 . When subjected to prolonged boiling, it combines with water, 

 giving rise to ammonium carbonate. The presence of Micrococcus urea 

 in urine will also convert the urea, by combining it with two molecules of 

 water, into ammonium carbonate, CON 2 H 4 + 2H 2 O = (NH 4 ) 2 CO 3 . 



The amount of urea excreted each day varies from 30 to 40 grams the 

 average being about 34 grams and therefore represents an amount of 

 protein metabolized equivalent to from 90 to 120 grams or an average 

 of about 100 grams., The remaining nitrogen-holding compounds in the 

 urine represent as shown by their nitrogen content a protein metabolism 

 of about 12 grams. As to how much of the urea or of the total nitrogen is 

 derived from the metabolism of tissue protein and how much from the 

 metabolism of the food protein that is not elaborated into tissue protein, 

 is difficult to state. It has been observed however in human beings in the 



