Once in a while a discovery changes the course of medicine and sometimes, the course of history itself. The Great Medical Discoveries series chronicles just such milestones. In clear, non-technical terms, the text describes how people coped before the discovery, the events leading to the discovery, the discovery itself and future directions in research. Germs are everywhere, as this overview of the subject explains. Some germs are harmful, causing debilitating disease, while others are beneficial, helping humans and animals to digest food. This volume explores the discovery of germs, how some cause disease, how others aid living things and how various industries have learned to use some germs to improve the quality of human life and communities.