Effect of too Little and of too Much Water. Amount of Water Used. Effect of Water in Health and Disease. Impurities in Water. Purification of Water. Kinds of Water.

Water is of the greatest importance for the maintenance of life. It constitutes about 60 per cent of the human body. S. Solis Cohen has rightly said that "the cells of the body are aquatic in their habit." They not only are composed largely of water, but are bathed by it more or less freely. Even the skin is coated at times with a perceptible, at other times with an imperceptible, film of it.

It enters into the chemical composition of the tissues. It constitutes much the largest proportion of all the fluids of the body. By keeping serous and mucus surfaces moist it prevents friction and the distress which their drying would cause. In the blood and lymph it helps to carry food to all parts of the body and to eliminate waste matter. It helps to distribute body heat and to regulate it by the physical processes of absorption and evaporation.

All living things soon die if deprived of water. Man can abstain from eating for weeks, but he cannot live and be deprived entirely of water for more than a very few days, and much distress is caused in a few hours. When abstinence from water is enforced, the first noticeable change is diminished secretion of fluid by various glands; therefore the skin, the mouth, the stomach, and the intestinal canal become abnormally dry. The free action of the kidneys is interfered with. Thirst is felt keenly. Next the tissues lose their water and the body diminishes rapidly in size and may even become emaciated. The muscles lose their power to act. The mind is affected, possibly in part from the drying of nerve tissues; probably chiefly from the failure to eliminate toxins naturally formed by tissues. Delirium develops, and finally coma and death ensue.