362 HANDBOOK OF PHYSIOLOGY. 



urates or free uric acid is deposited. After a time, varying in length ac- 

 cording 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 ureae). The urea 

 takes up two molecules of water a strong ammoniacal and foetid odor 

 appears, and deposits of triple phosphates and alkaline urates take place. 

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

 least, until air has had access to it. 



Reaction of Urine in different classes of Animals. In most herbivo- 

 rous animals the urine is alkaline and turbid. The difference depends, 

 not on any peculiarity in the mode of secretion, but on the differences 

 in the food on which the two classes subsist; for when carnivorous ani- 

 mals, such as dogs, are restricted to a vegetable diet, their urine becomes 

 pale, turbid, and alkaline, like that of an herbivorous animal, but re- 

 sumes its former acidity on the return to an animal diet ; while the 

 urine voided by herbivorous animals, e.g., rabbits, fed for some time ex- 

 clusively upon animal substances, presents the acid reaction and other 

 qualities of the urine of Carnivora, its ordinary alkalinity being restored 

 only on the substitution of a vegetable for the animal diet. Human 

 urine is not usually rendered alkaline by vegetable diet, but it becomes 

 so after the free use of alkaline medicines, or of the alkaline salts with 

 carbonic or vegetable acids; for these latter are changed into carbonates 

 previous to elimination by the kidneys. 



Average daily quantity of the chief constituents of the Urine 



(by healthy male adults}. 



Water, 52. fluid ounces. 



Urea, 512.4 grains. 



Uric acid, 8.5 



Hippuric acid, uncertain, probably 10 to 15. " 



Sulphuric acid 31.11 " 



Phosphoric acid, .... 45. "' 



Potassium, Sodium, and Ammonium ) ^^ ^5 

 Chlorides and free Chlorine, . j 



Lime 3.5 " 



Magnesia, 3. " 



Mucus, 7. 



f Kreatinin, "1 



Extractives, \ S^SS* 



Adncnin, i -^^ t< 



{ Hypoxanthin, 

 Resinous matter, 

 etc., 



Variations in the Quantity of the Constituents. From the 

 proportions given in the above table, most of the constituents are, even 

 in health, liable to variations. The variations of the water in different 

 seasons, and according to the quantity of drink and exercise, have al- 

 ready been mentioned. The water of the urine is also liable to be influ- 



