332 PHYSIOLOGICAL CHEMISTRY. 



yellowish-brown, rose-colored, or often brick-red precipitate (sedi- 

 mentum latentium) settles on cooling because of the greater insolu- 

 bility of the urates at the ordinary temperature than at the temper- 

 ature of the body. This cloudiness disappears on gently warming. 

 In new-born infants the cloudiness of the urine during the first 

 4-5 days is due to epithelium, mucus-corpuscles, uric acid, and 

 urates. The urine of herbivora, which is habitually neutral or 

 alkaline in reaction, is very cloudy on account of the carbonates of 

 the alkaline earths present. Human urine may sometimes be 

 alkaline under physiological conditions. In this case it is made 

 cloudy by the earthy phosphates, and this cloudiness does not dis- 

 appear on warming, differing in this respect from the sedimvntum 

 lateritium. Urine has a salty and faintly-bitter taste produced by 

 sodium chloride and urea. The odor of urine is peculiarly aro- 

 matic; the bodies which produce this odor are unknown. 



The color of urine is normally pale yellow when the specific 

 gravity is 1.020. The color otherwise depends on the concentration 

 of the urine and varies from pale straw-yellow, when the urine 

 contains small amounts of solids, to a dark reddish yellow or reddish 

 brown in stronger concentration. As a rule, the intensity of the 

 color corresponds to the concentration, but under pathological 

 conditions exceptions occur, and such an exception is found in 

 diabetic urine, which contains a large amount of solids and has a 

 high specific gravity and a pale yellow color. 



The reaction of urine depends essentially upon the composition 

 of the food. The carnivora void an acid, the herbivora a neutral 

 or alkaline, urine. -If a carnivora is put on a vegetable diet, its 

 urine may become less acid or neutral, while the reverse occurs 

 when an herbivora is starved, that is, when it lives upon its own 

 flesh, as then the urine voided is acid. 



The urine of a healthy man on a mixed diet has an acid reaction, 

 and the sum of the acid equivalents is greater than the sum of the 

 base equivalents. This depends on the fact that in the physiolog- 

 ical burning of neutral substances (proteids and others) within 

 the organism acids are produced, chiefly sulphuric acid, but also 

 phosphoric and organic acids, such as hippuric, uric, and oxalic 

 acid, also aromatic oxyacids and others. From this it follows that 

 the acid reaction is not due to one acid alone. We do not know to 



