Across the ages, human beings have tried to prolong life and evade senility by magical, religious, and scientific means. In modern times, the role of science has naturally been preeminent. For a time during the early decades of this century, scientists indeed seemed to have discovered a number of methods to conquer senility. Appearances, unsurprisingly, were deceptive, and the entire episode was soon forgotten. Neither scientists nor historians have devoted much attention to the topic, and only a few historical studies are available [1][2]. Contemporary scientists or physicians think of this subject, if at all, as part of the history of quackery or, at best, of the gullibility of scientists.Closer historical examination reveals this view to be simplistic. To be sure, rejuvenation research had its share of cranks and charlatans. Even the serious scientists in the area were frequently unsound in their methods and drew hasty, wish-fulfilling conclusions. It is unfair, however, to overlook that these flaws notwithstanding, much of this research was conceived along accepted scientific doctrine of the time. The history of rejuvenation research, like the history of science in general, reveals a complex interplay of rationality, gullibility, and sheer folly.