"Human beings are made up mostly of water, in roughly the same percentage as water is to the surface of the earth.  Our tissues and membranes, our brains and hearts, our sweat and tears--all reflect the same recipe for life, in which efficient use is made of those ingredients available on the surface of the earth. We are 23 percent carbon, 2.6 percent nitrogen, 1.4 percent calcium, 1.1 percent phosphorous, with tiny amounts of roughly three dozen other elements.  But above all we are oxygen (61 percent) and hydrogen (10 percent), fused together in the unique molecular combination known as water, which makes up 71 percent of the human body."