452 THE URINE. 



of food or drink ; if it be not used, the whole of the urine 

 passed during a. period of twenty* four hours should be 

 taken. In accordance with the various circumstances 

 above-mentioned, the specific gravity of the urine may, 

 consistently with health, range widely on both sides of 

 the usual average. The average healthy range may be 

 stated at from 1015 in the winter to 1025 in the summer 

 (Prout), and variations of diet and exercise may make as 

 great a difference. In disease, the variation may be 

 greater; sometimes descending, in albuminuria, to 1004, 

 and frequently ascending in diabetes, when the urine is 

 loaded with sucav, to 1050, or even to 1060 (Watson). 



The whole quantity of urine secreted in twenty-four 

 hours is subject to variation according to the amount of 

 fluid drunk, and the proportion of the latter passing off 

 from the skin, lungs, and alimentary canal. It is because 

 the secretion of the skin is more active in summer than in 

 winter, that the quantity of urine is smaller, and its 

 specific gravity proportionately higher. On taking the 

 mean of numerous observations by several experimenters, 

 Dr. Parkes found that the average quantity voided in 

 twenty-four hours by healthy male adults from twenty to 

 forty years of age, amounted to 5 z\ fluid ounces. 



Chemical Composition of the Urine. 



The urine consists of water, holding in solution certain 

 animal and saline matters as its ordinary constituents, and 

 occasionally various matters taken into the stomach as 

 food salts, colouring matter, and the like. The quan- 

 tities of the several natural and constant ingredients of 

 the urine are stated somewhat differently by the different 

 chemists who have analysed it ; but many of the differences 

 are not important, and the well-known accuracy of the 

 several chemists renders it almost immaterial which of the 

 analyses is adopted. The analysis by A. Becquerel being 

 adopted by Dr. Prout, and by Dr. Golding Bird, will be 

 here employed. (Table I.) 



