GENERAL CHARACTERISTICS OF THE URINE. 211 



apparently healthy individuals in consequence of certain abnormali- 

 ties of metabolism (see page 261). The urine may then be of a 

 normal color when recently passed, but soon darkens on standing, 

 and finally appears almost black. In diabetes a light color may be 

 associated with a high specific gravity. 



The odor of recently passed urine is peculiarly aromatic, and is 

 probably referable to the presence of several volatile acids. Decom- 

 posing urine has a characteristic odor, which is in part due to 

 ammonia. 



Amount. The amount of urine eliminated in the twenty-four 

 hours is quite variable even under normal conditions. It is, of 

 course, primarily dependent upon the amount of water ingested, but 

 is also influenced by the character and the quantity of the food, the 

 process of digestion, the blood-pressure, the surrounding tempera- 

 ture, the emotions, sleep, exercise, body-weight, sex, age, etc. It 

 must hence differ in different countries, according to the habits of 

 the people, the climate, etc., and we accordingly find that different 

 observers give different figures. In Germany and Austria, where 

 much beer is consumed, from 1500 to 2000 c.c. are regarded as 

 average amounts. In England 1000 to 1500 c.c. are regarded as 

 normal ; in France, 1250 to 1300 c.c. 



In this country I have found that the average daily amount is 

 somewhat lower, and am inclined to regard an elimination of from 

 1000 to 1200 c.c. as normal for men, while in women a somewhat 

 smaller quantity is normally passed. Children pass absolutely less 

 but relatively more urine, as compared with their body-weight, than 

 adults. 



In the summer-time, when the sweat-glands are especially active, 

 and when larger amounts of water are eliminated through the lungs 

 and the skin, the secretion of urine is proportionately less, but rarely 

 falls below 800 c.c. unless active exercise is indulged in at the same 

 time. 



During repose, moreover, much less urine is voided than when 

 exercise is taken, and we hence find a smaller secretion of urine 

 during the night than during the day. The maximum secretion is 

 usually observed a few hours after the midday meal. 



Artificially, the secretion can be increased by the ingestion of 

 those articles of food which tend to increase the blood-pressure, such 

 as coffee, tea, and alcohol. Many drugs also bring about the same 

 effect, though the modus operandi of each is not known. The most 

 important medicinal diuretics are digitalis, squill, broom, juniper, 

 nitrous ether, urea, etc. Distilled water also has distinct diuretic 

 properties. 



In disease, and notably in diabetes mellitus, diabetes insipidus, 

 and chronic interstitial nephritis, the amount of urine may far sur- 

 pass the usual quantity, and may indeed exceed 10,000 c.c. in the 

 twenty-four hours (polyuria). Abnormally small amounts, on the 

 other hand (oliguria), are observed in the acute febrile diseases, in 



