The urine secreted by the kidneys is a body excretion, and consists of water, organic matter and salts. The nitrogenous end-products, aromatic compounds, coloring matter, and mucin form the organic matter. The nitrogenous end-products and aromatic compounds are urea, uric and hippuric acids, benzoic acid and ethereal sulfates of phenol and cresol. The salts are sulfates, phosphates and chlorides of sodium, potassium, calcium and magnesium. The organic and inorganic matter varies with the ration. The quantity of urine secreted within a given time varies in the different species and at different times in the same individual. In the horse the quantity secreted in twenty-four hours varies from twelve to fifteen pints; in cattle from ten to forty pints; in sheep from one-half to one and three-quarter pints. The normal color of the urine varies. In the horse it is yellow or yellowish-red; in cattle and sheep yellowish; and in the dog a straw yellow. The specific gravity varies with the quantity secreted and the ration fed. When the quantity of urine secreted is above the average, the specific gravity is usually low. THE NECESSITY OF EXAMINING THE URINE.--In diseases of the urinary apparatus, a careful examination of the urine is very necessary in order to be able to form a correct diagnosis. In domestic animals it is impractical to attempt to determine the exact amount of urine passed within a certain time, but we can make a general estimate of the quantity passed by carefully observing the animal and noting the condition of the bedding in the stall. The sample of urine to be examined is best taken from urine collected at different periods during the day. We should note its color and consistency. The different substances in the urine can be determined only by determining the specific gravity, testing with certain chemical reagents and by making a microscopic examination of the sediment. Normal urine from the horse may be turbid or cloudy and more or less slimy, because of the presence of mucin. This is less true of other species. In disease the color of the urine may be changed to a pale yellow, red or brown. For example, in congestion of the kidneys the urine is light in color and rather transparent; in southern cattle fever it may be red; and in azoturia it may be brown. EXCESSIVE URINATION.--The horse is the most common sufferer from excessive secretion of urine. The most common _causes_ are musty feeds, such as hay, grain and shipped feeds. New oats, succulent feeds and acrid plants may sometimes cause it. In the fall of the year, when the season is changing from warm to cool weather and the horse eliminates less water from the body by way of the skin, the kidneys may become more active and the quantity of urine secreted be greatly increased. This, however, is a normal physiological condition and should not be confused with this disease.