428 EXCRETION 



The total quantity of urine passed in twenty-four hours is influenced 

 by numerous circumstances. In adults of average size and medium ac- 

 tivity the daily amount of urine may be given as from 1,200 cc. to 1,500 cc. 

 In Chittenden's recent observations on nine athletic students and on eight 

 soldiers the average daily output of urine through a period of about five 

 months was for the students 1,215 cc. with average specific gravity of i .020, 

 and for the soldiers 1,042 cc. with specific gravity of i .023. 



GENERAL CHEMICAL COMPOSITION OF THE URINE. 



Water 967 



Solids: 



Urea 14.230 



Other nitrogenous crystalline bodies: 



Uric acid, principally in the form of alkaline urates, 



a trace only free 



Kreatinin, xanthin, hypoxanthin f 



Hippuric acid 



Mucus, pigments, and ferments 



Salts: 



Inorganic: 



Principally sulphates, phosphates, and chlorides 

 of sodium and potassium, with phosphates 

 of magnesium and calcium, traces of silicates 

 Organic: 



Lactates, oxalates, acetates, butyrates and for- 

 mates, which appear only occasionally. . . . j - 33 



Sugar a trace sometimes. 



Gases (nitrogen and carbon dioxide principally). 



1,000 



Reaction. The normal reaction of the urine is slightly acid. This 

 acidity is due to carbon dioxide and to acid phosphate of sodium, and is less 

 marked soon after meals. After a time, varying in length according to the 

 temperature, the reaction becomes strongly alkaline from the change of 

 urea into ammonium carbonate, due to the presence of one or more specific 

 micro-organisms (micrococcus urea). In the process of fermentation the 

 urea takes up two molecules of water, a strong ammoniacal and fetid odor 

 appears, and there are deposits of triple phosphates and alkaline urates. 

 This does not occur unless the urine is freely exposed to the air, or, at least, 

 until air has had access to it. 



In most herbivorous animals the urine is alkaline and turbid. The 

 difference depends not on any peculiarity in the mode of secretion, but on 

 the difference in the food on which the two classes of animals subsist. For 

 when carnivorous animals, such as dogs, are restricted to a vegetable diet, 

 their urine becomes pale, turbid, and alkaline like that of herbivorous 

 animals, while the urine voided by the herbivora, e.g., rabbits, fed for some 



