Microbe Hunters was the title of a wonderfully successful science-popularzing book written by Paul de Kruif and published by Simon & Schuster in 1926. The book is on its face a set of capsule biographies of prominent biologists from Leeuwenhook to Paul Ehrlich. Leeuwenhook invented the microscope: Ehrlich found a cure for syphilis in 1909. But de Kruif had an underlying organizing principle by which he made his selection. The book was about the pragmatic successes of the germ theory of disease. Specifically, a 'typical' disease has one cause, and the cause is usually a germ. The way to cure (or immunize people from) a disease is to find the germ that causes it, then either(a) find a way to kill that microbe without doing damage to the surrounding tissue (a "magic bullet" as Ehrlich called such a discovery) or find a way to assist the body's own immune system in doing the same. Hence, the title of the book. The only character in the book to get two chapter...