Nobody has quite found the fountain of youth. But a number of reputable gerontologists feel they are close to discovery of the biological mechanism that regulates aging. Such a discovery would be used to prolong youthfulness and, ultimately, life. Prehoda, who likes to write roundups of young sciences (Designing the Future. 1967), outlines the latest experiments with enzymes, hormones, nutrition, and cellular therapy. He also supplies an explanation of each of the three major theories of senescence: cross-linkage, somatic mutation, and autoimmunic reaction. Unfortunately, they are best understood by molecular biologists and chemists and, possibly, by a few very interested laymen. The data on how and why senility occurs and on how aging affects the mind and body (particularly sexual capacity) is less esoteric, and, of course, is readily available in other books. The strength of Prehoda's book is its no-nonsense approach to a flashy subject. It focuses on the fact that scientists are no longer so skeptical about finding that elusive fountain. They remember that Schliemann found Troy even if it wasn't quite what he thought.