THE URINE. 147 



rare will be spoken of later. All of these either are taken 

 as such into the body with the food or are formed in the 

 body by chemical action. The significance of each may 

 depend upon the amount which is present, as well as upon 

 its mere presence or absence. In interpreting the mean- 

 ing of each of the constituents of the urine its method of 

 formation must be considered, as well as the factors which 

 may cause this to vary. 



Considerable variations are found in the composition 

 of urine which has been collected at different times of the 

 day. That which is passed immediately after rising may 

 differ from that excreted an hour or two after the first 

 meal both in the kind and amount of the dissolved solids. 

 Sugar and albumin are more commonly excreted after a 

 meal, and may be found then, yet not be present in the 

 night's urine. In order to obtain a fair sample for testing, 

 the urine should be collected for twenty-four hours and, 

 after mixing, a part taken for analysis. In all quantitative 

 determinations the volume for twenty-four hours must be 

 measured, and when it has been determined how much of 

 the substance is present in the portion tested, the amount 

 contained in the whole day's urine should be calculated. 

 A statement of the percentage alone has little value if the 

 quantity of the urine is not taken into account. To avoid 

 fermentation the vessels should be clean and the tests 

 should be made as soon as possible. 



The average volume of the urine in twenty-four hours 

 is, for an adult, between 900 cubic centimeters and 1200 

 cubic centimeters (30 and 40 ounces). This, however, is 

 subject to great variations. It is increased by diuretics, by 

 diseases, like diabetes and others; it is diminished in febrile 

 diseases, in acute nephritis, in some other diseases of the 

 kidneys, and usually before the fatal termination of a dis- 



