1080 EXCRETION 



CHAPTER XCI 

 THE COMPOSITION OF THE URINE 



General Characteristics of Urine. ^ — The urine of man is a clear, 

 fluorescent fluid, the color of which varies from light yellow to dark 

 yellow in accordance with its content in pigmentous material. The 

 latter consists chiefly of urochrome, which is composed of 11.1 per cent, 

 of nitrogen and 5 per cent, of sulphur, and is in all probability derived 

 from protein. Urobilin, another pigment, is present in normal urine 

 in only very small quantities. It is derived from the coloring mate- 

 rial of the bile which is converted in the intestines into stercobilin. 

 While the latter leaves the body principally in the feces, some of it 

 is reabsorbed to be finally excreted in the urine. Its mother-sub- 

 stance, known as urobilinogen, is present in somewhat greater quanti- 

 ties and is easily oxidized into urobilin proper. The pink coloring 

 material of the urates is uroerythrin. A trace of hematoporphyrin 

 is also present normally. 



The odor of urine depends upon the quality of the food ingested. 

 When meat, bread and butter are taken, it is not at all unpleasant. 

 A most peculiar odor is imparted to it by asparagus. To the taste urine 

 is bitter and salty. The quantity of urine varies considerably, and de- 

 pends upon the intake of water and the proportion of it which is ex- 

 creted through other channels, such as the intestines, sweat glands and 

 respiratory passage. Under ordinary conditions, from 1400 to 1800 

 c.c. are voided in the course of twenty-four hours, the smallest portion 

 of this amount being excreted during the night. If a reverse relation- 

 ship exists so that the person must micturate during the night, sus- 

 picions of renal disease should be aroused, but naturally, only if moder- 

 ate amounts of water and other fluids have been taken on the 

 evening preceding. . 



The specific gravity of the urine varies greatly in different persons as 

 well as in the same person at different times of the day. The chief 

 factor tending to vary its value is the proportion of water to the amount 

 of solids ingested, and the relationship between the activity of the 

 kidneys and that of the other excretory channels. Under ordinary 

 conditions, values between 1.015 and 1.025 are encountered, while 

 a constant value of 1.010 and less would point toward the presence 

 of hydruria, and one of 1.030 and over, toward diabetes. Temporary 

 variations of this kind, however, are common and may easily be pro- 

 duced by an intake of large quantities of water or by profuse sweating. 



1 For a more detailed discussion the reader is referred to Mathew's Biological 

 Chemistry, Hamburger's Osm. Druck and Jonenlehre, and Oppenheimer's Handb. 

 der Biolog. Chemie. 



