The subject is longevity. There are two basic factors involved in increasing the average life expectancy of man. The first is based on the elimination of diseases and unhealthy environments which prevent people from living out their full span of life, and practically all progress in the field has been along these lines. The other, which is much more tentative, deals with the actual lengthening of the possible life span. The opening chapter suggests some of the possibilities for experimentation along these lines, and it is a disappointment that this exciting new area is not investigated further in the book until the ending, which barely touches upon the implications (what are the factors that cause an organism to wear out, why do different species have such varying life spans, how would increasing age affect the population, etc.). Most of the book is a short survey of medical discoveries, sanitary developments and their implementation, and the like. The text is in a very readable form, but the material is not terribly well organized and a lot has been covered in much greater detail in countless other medical and social histories for this age group. By the author of This is Automation and The Globe for Space Age.