356 THE URINE. 



The Urine : its General Properties. 



Healthy urine is a clear limpid fluid, of a pale yellow or 

 amber color, with a peculiar faint aromatic odor, which be- 

 comes pungent and ammoniacal when decomposition takes 

 place. The urine, though usually clear and transparent at 

 first, often becomes as it cools opaque and turbid from the de- 

 position of part of its constituents previously held in solution ; 

 and this may be consistent with health, though it is only in 

 disease that, in the temperature of 98 or 100, at which it is 

 voided, the urine is turbid even when first expelled. Although 

 ordinarily of pale amber color, yet, consistently with health, 

 the urine may be nearly colorless, or of a brownish or deep 

 orange tint, and, between these extremes, it may present every 

 shade of color. 



When secreted, and most commonly when first voided, the 

 urine has a distinctly acid reaction in man and all carnivorous 

 animals, and it thus remains till it is neutralized or made alka- 

 line by the ammonia developed in it by decomposition. In 

 most herbivorous animals, on the contrary, the urine is alka- 

 line and turbid. The difference depends, not on any peculi- 

 arity 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 her- 

 bivorous animal, but resumes its former acidity on the return 

 to an animal diet; while the urine voided by herbivorous ani- 

 mals, 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 (Bernard). 

 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 previous to 

 elimination by the kidneys. Except in these cases, it is very 

 rarely alkaline, unless ammonia has been developed in it by 

 decomposition commencing before it is evacuated from the 

 bladder. 



The average specific gravity of the human urine is about 

 1020. Probably no other animal fluid presents so many va- 

 rieties in density within twenty-four hours as the urine does ; 

 for the relative quantity of water and of solid constituents of 

 which it is composed is materially influenced by the condition 

 and occupation of the body during the time at which it is se- 

 creted, by the length of time which has elapsed since the last 



