356 HAND-BOOK OF PHYSIOLOGY. 



less marked after meals. The urine contains no appreciable amount u of 

 free acid, as it gives no precipitate with sodium hyposulphite. After 

 standing for some time the acidity increases from a kind of fermentation, 

 due in all probability to the presence of mucus, and acid urates or free 

 uric acid is deposited. After a time, varying in length according to the 

 temperature, the reaction becomes strongly alkaline from the change of 

 urea into ammonium carbonate while at the same time a strong ammoni- 

 acal and foetid odor appears, with deposits of triple phosphates and alka- 

 line urates. As this does not occur unless the urine is exposed to the 

 air, or, at least, until air has had access to it, it is probable that the de- 

 composition is due to atmospheric germs. 



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 animals, 

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

 turbid, and alkaline, like that of an herbivorous animal, but resumes its 

 former acidity on the return to an animal diet; while the urine voided by 

 herbivorous animals, e.g., rabbits, fed for some time exclusively 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 alkaline carbonates pre- 

 vious to elimination by the kidneys. 



AVERAGE QUANTITY OF THE CHIEF CONSTITUENTS OF THE URINE 

 EXCRETED IN 24 HOURS BY HEALTHY MALE ADULTS (PARKES). 







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, Ammonium Chlorides ) 323-25 " 

 and free Chlorine . . . . j 



Lime 3'5 



Magnesia 3* 



Mucus 7* " 



{Kreatinin 

 Sffin } . . 154- 



Hypoxanthin 

 Eesinous matter, etc. 



Variations in Quantity of Constituents. From these proportions, 

 however, most of the constituents are, even in health, liable to variations. 



