Specific gravity: The morning urine is best calculated for analysis. The average healthy range may be stated at 1015 in the winter to 1025 in the summer, and variations of diet and exercise may make a great difference. In disease, the variations may be greater; sometimes descending in albuminaria to 1004, and frequently ascending in diabetes, when the urine is loaded with sugar, to 1050, or even to 1060. The whole quantity of urine secreted in twenty-four hours is subject to variations according to the amount of fluid drunk, and the proportion of the latter passing off from skin, lungs, and alimentary canal. The average quantity voided in twenty-four hours by healthy male adults from twenty to forty years of age amounts to 52 1/2 fluid ounces. The chemical composition of urine. The average quantity of each constituent of the urine in 1,000 parts is: Water (O H2), 967 Urea (C O N2 H4), 14.239 Uric acid (C5 N4 H4 O3), .468 Coloring matter, mucus, and animal extractive matter, 10.107 { Sulphates (soda, potash), } 8.185 Salts. { Bisulphates (lime, soda, } { magnesia, ammonia), } { Chlorides (sodium, potassium), } Silica, etc., Traces. --------- 1,000.000 Urea is the principal solid constituent of the urine, forming nearly one-half of the whole quantity of solid matter. It is also the most important ingredient, since it is the chief substance by which the nitrogen of decomposed tissue and superfluous food is excreted from the body. The salts excreted by the kidneys in 24 hours are: Urea (C N2 H4 O), 512 grains. Chloride of sodium (Na Cl), 177   ,,    Phosphoric acid (H3 P O4), 48   ,,    Sulphuric acid (H2 S O4), 31.11   ,,    Uric acid (C5 N4 H4 O3), 8.53   ,,    The substances excreted consist mainly of carbonic acid gas (C O2), which is expired by the lungs, and urea (C N2 H4 O), which is expelled by the urine. These excretions, or expenditures, or waste products of the human body, present the carbohydrates--starch, sugars, and fats--and the proteids--meats and albumen--taken into the system as food. The daily average loss by the expenditure or waste products of the body is estimated to be about: Carbon, 4,500 grains. Nitrogen, 3 to 500 grains. Besides salts and water.