The human body is constantly throwing off water. A large portion is lost by evaporation from the skin, upon which it is poured out by millions of what might be termed little sewer pipes or sweat ducts, for the purpose of washing away impurities from the system. The kidneys remove a considerable quantity, bearing with it poisonous elements in solution, the product of various vital activities. In other ways water is removed from the body, to the amount of about five pints in twenty-four hours. This loss must be made good in order that the requisite fluidity of the blood shall be maintained; and the need of the body is expressed by thirst. Beverages which contain other substances, as flavor, or as part of some mixed drink, are useful as thirst quenchers just in proportion to the amount of water which they contain. Physiologists point to the evaporation of water from the surface of the human body as being one of the most perfect adaptations of means to ends exhibited in the whole circle of life. The vital activities of the body occasion the constant production of heat. At times the heat is greater than is needed, and would destroy the vitality of certain tissues if it were not speedily conducted away, just as too much heat in a stove would melt the iron of the stove. The evaporation of water from the skin accomplishes this heat dispersal. When external heat is great, perspiration in the normal, healthy person is more active than when external heat is less than that in the body, and, by this provision of Nature, the temperature of the body is maintained at about 100° Fahrenheit under all circumstances, and thus man is enabled to exist under such great extremes of heat and cold as are found in nature.