Today, a fever is an uncomfortable nuisance, but a hundred-plus years ago, fevers were often fatal. The difference between then and now is the class of drugs known as antibiotics. As the name implies, “anti-biotics” work “against life,” or, more specifically, against living cells. While other drugs, such as aspirin, ease the symptoms of a disease, antibiotics attack the living bacteria that are causing the symptoms. The modern discovery of antibiotics is usually attributed to Alexander Fleming, who was the first to isolate and name “penicillin.” But the basis for Fleming’s work had begun over fifty years before. In 1874, another English scientist, William Roberts, noticed that some fungi were immune to bacteria. Later on, the French scientist Louis Pasteur noticed that bacteria stopped growing if they became infected with a microscopic fungus called “penicillium.”