674 URINE. * 



amount is nearly as large as in the blood-serum. Urea occurs sometimes in 

 considerable amounts when the parenchyma of the kidneys is only in part atro- 

 phied; in complete atrophy the urea may be entirely absent. 



I. PHYSICAL PROPERTIES OF URINE. 



Consistency, Transparency, Odor, and Taste of Urine. Under 

 physiological conditions urine is a thin liquid and gives, when shaken 

 with air, a froth which quickly subsides. Human urine, or urine from 

 earnivora, which is habitually acid, appears clear and transparent, often 

 faintly fluorescent, immediately after voiding. When allowed to stand for 

 a little while human urine shows a light cloud (nubecula), which consists of 

 the so-called '''mucus," and generally also contains a few epithelium 

 cells, mucus-corpuscles, and urate-granules. The presence of a larger 

 quantity of urates renders the urine cloudy, and a clay-yellow, yellowish- 

 brown, rose-colored, or often brick-red precipitate (sedimentum lateri- 

 tium) settles on cooling, because of the greater insolubility of the urates 

 at the ordinary temperature than at the temperature 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 cloudy, due to the earthy phosphates, and this cloudiness does not 

 disappear on warming, differing in this respect from the sedimentum 

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

 chloride and urea. The odor of urine is peculiarly aromatic; 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 con- 

 centration. As a rule the intensity of the color corresponds to the con- 

 centration, but under pathological conditions, exceptions occur such as 

 are 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 earnivora, as a rule, void an acid, the herbivora, a neutral 

 or alkaline urine. If a carnivore is put upon a vegetable diet, its urine 

 may become less acid or neutral, while the reverse occurs when an herbi- 

 vore is starved, that is, when it lives upon its own tissues, as then the 

 urine voided is acid. 



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



