Biologist Edward Golub's book "The Limits of Medicine," explores the history of medical advances and argues that medicine's new goal should be to extend health, not life span. There will be no "magic bullet" for today's major illnesses like there was for earlier scourges like polio, smallpox and diphtheria, he says. Golub was a professor of biology at Purdue University for twenty years and a director of research in the pharmaceutical industry for five years.