180 PHYSIOLOGICAL CHEMISTRY 



The total solids excreted in the course of a day will vary 

 considerably. Sixty grams is an average figure. The amount de- 

 pends largely upon the amounts of sodium chloride and pro- 

 tein eaten, for NaCl and urea, the principal end product of 

 protein metabolism in the body, make up the largest part of the 

 total solids. (For the estimation of total solids see the labora- 

 tory directions.) 



Optical Activity, Reducing Power, Fermentation, Etc. 

 Normal urine is slightly levorotatory, since it contains minute 

 traces of protein and of conjugated glucuronates, both of which 

 rotate strongly to the left. It contains also minute traces of 

 glucose, which is dextrorotatory, but the amount is too small to 

 counteract the levorotatory substances. 



Pathological urine may show strong rotation. If dextrose is 

 present the rotation will be to the right. If protein or levulose 

 are present in quantity, the rotation will be to the left, as is also 

 the case if the urine contains large amounts of conjugated glu- 

 curonates, as it does after taking camphor, chloral hydrate, 

 menthol and various other drugs. 



Normal urine has a slight reducing power, due to its content 

 of traces of sugar, of conjugated glucuronates, uric acid and 

 other substances. The reduction is not sufficient to interfere in 

 the ordinary Fehling test when small amounts of urine are used 

 however, so that this test, as performed with normal urine is 

 negative. In pathological urine, particularly carbohydrate 

 urine, the reduction may be extensive, and is made use of to 

 detect sugar. 



On standing, urine may ferment in a variety of ways as the 

 result of the activities of microorganisms. Ammoniacal fer- 

 mentation is the most common. Micrococcus urese and B. ureae 

 decompose the urea, forming ammonia. The urine becomes alka- 

 line, its color changes, and phosphates, etc., are precipitated. 

 Dilute urine usually ferments quicker than a concentrated 

 specimen. A strong acid reaction retards the process. Other 

 types of fermentation also occur. 



Pathological urines usually ferment quicker than normal 



