Ranking with the soil and the atmosphere, water is recognized as being one of the absolute essentials of existence. We are all familiar with the fact that where water is absent - or unavailable, which is equivalent - life likewise is absent or nearly so. It is difficult, perhaps needless, to decide which is the most necessary, soil, air, or water, all are so intimately interwoven into the complex relationships of life. Not only is that water which is exterior to the organic creation an essential to the continued well-being of that creation but much the greater bulk of animal and vegetable tissue is composed of water. It is estimated that of annual plants, three-fourths of the substance is water; of perennials, three-eighths is water. Eighty per cent of animal tissue is water, and this ratio holds good with regard to the body of man himself. The gray matter of the human brain - the most highly developed and specialized living material on the planet - is said to consist of 83.5 per cent of water leaving only 16.5 per cent of solid matter, so called (Van Hise).
Proceedings of the Iowa Academy of Science
©1920 Iowa Academy of Science, Inc.
Lees, James H.
"The Conservation of Underground Waters,"
Proceedings of the Iowa Academy of Science, 27(1), 187-196.
Available at: https://scholarworks.uni.edu/pias/vol27/iss1/26