In this illuminating chronicle of the progress of medicine in understanding and battling infectious diseases, Glasser links the work of today's immunologists, microbiologists, and virologists with the struggles of earlier medical pioneers. Glasser (The Greatest Battle, 1976, etc.) honors the clear-thinking men--Jenner, Semmelweis, Pasteur, and Koch, among others--whose observations challenged the accepted medical dogma of their day and finds telling parallels in more recent events. As he sees it, the refusal in the 1980s of blood-bank officials to consider that their plasma supplies might be contaminated with HIV echoes the refusal of hospital physicians in Semmelweis's day to believe their unwashed hands were causing childbed-fever deaths. Medicine has never done well, Glasser says, when ""dismissing focused observations or ignoring scientific fact . . . and nowhere has this been more obvious than in the study of infections and the relationship of infectious disease to the world of cells, cellular function, and DNA."" Glasser takes the reader into that world by going back to the very beginnings of life on this planet. The idea that the fundamental unit of life was the cell, is, he says, a prejudice that still exists today. What he focuses on are viruses, minute crystal-like structures, less than one ten-thousandth the diameter of a cell, that evolved along with cellular life, may even have shaped the way cells evolved, and are today recognized as the causes of devastating diseases. More recently, a new kind of infectious disease was discovered when ""mad cow"" disease was found to be transmitted not by a virus but by special proteins called prions. It was, for Glasser, yet another demonstration of observation beating dogma and authority. A well-conducted tour for those curious about genes, viruses, DNA, and our mysterious immune system.