Water is formed into the solid state, ice, at zero degrees centigrade. At 100° C. water boils and is converted into gas or vapor, although water is contained in the air in the gaseous form at ordinary temperatures. Between these two limits, 0° C. and 100° C. water obtains in the liquid form which is its most common state. Water is the most widely distributed of all the substances. It is practically incompressible. When heated it contracts until it reaches 4° C, or 39.2° F., and is at this point taken as the basis for specific gravity of liquids and solids. Universal Solvent Water is the most universal solvent known in Nature. Practically all substances yield to it. Most of the water taken into the body passes through unchanged, although it is only reasonable to suppose that some of it is broken up into its elements and united with other compounds of the body. Necessity for Water in Body Water composes about 70% of the entire weight of the body (about 58.5% per volume). A very great amount of water is required by the tissue for the performance of the bodily functions. As the gears of machinery must be bathed in oil to prevent undue wear, so must the tissue cells be bathed in water (secretions) that there be no undue wear. The tissue cells are spoken of as being aquatic in their habits. Rosenau in summarizing the use of water in the body says: “It enters into the chemical composition of the tissues; it forms the chief ingredient of all the fluids of the body and maintains their proper degree of dilution, and thus favors metabolism; by moistening various surfaces of the body, such as mucous and serous membranes, it prevents friction; it furnishes in the blood and lymph a fluid medium by which food may be taken to remote parts of the body and the waste material removed, thus promoting rapid tissue changes; it serves as a distributor of bodily heat; it regulates the body temperature by the physical process of absorption and evaporation.” Chemically Pure Water Chemically pure water can be obtained only by distillation; it is undesirable, however, for drinking purposes because of its insipidity. Before such water is agreeable for drinking it must be aerated; this may be accomplished by agitation or by passing it through a porous substance containing air. One of Nature’s methods of aerating water is found in mountain streams where the water flows down over rocks. The same thing is accomplished by fountains and waterfalls. It is the mineral matter and the gases held in solution that give water its taste, and it is the difference in these minerals and gases that causes the individual to dislike the taste of water which he is not accustomed to drinking. But this is purely a matter of taste and has no value from a hygienic standpoint, for the most impure water, water that contains so-called pathogenic germs, may taste very good.