470 HANDBOOK OF PHYSIOLOGY. 



CHEMICAL, COMPOSITION OP THE URINE. 



Water 967 



Solids- 

 Urea . 14.230 



Other nitrogenous crystalline bodies ] 



Uric acid, principally in the form of alka- | 



line Urates, a trace only free. 10 gg 5 



Kreatinin, Xanthin, Hypoxathin. 

 Hippuric acid. 



Mucus, Pigments, and Ferments. J 



Salts : 



Inorganic 



Principally Sulphates, Phosphates, and 

 Chlorides of Sodium and Potassium, with 

 Phosphates of Magnesium and Calcium, 

 traces of Silicates and Chlorides. 



8.135 

 Organic 



Lactates, Hippurates, Oxalates, Acetates and 

 Formates, which only appear occasion- 

 ally. 



Sugar a trace sometimes. 



Gases (nitrogen and carbonic acid principally) . 



1000 



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

 acidity is due to acid phosphate of sodium, and is less marked soon after 

 meals. The urine contains no appreciable amount of free acid, as it 

 gives no precipitate of sulphur with sodium hyposulphite. After stand- 

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

 due in all probability to the presence of mucus and fungi, 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, due to the presence 

 of one or more specific micro-organisms (micrococcus urece). The urea 

 takes up two molecules of water a strong ammoniacal and foatid 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 herbivorous ani- 

 mals 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 subsist ; for when carnivorous animals, such as dogs, are re- 

 stricted 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 reac- 

 tion and other qualities of the urine of Garni vora, 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 car- 



