Louis Pasteur (1822–1895) was a French chemist and biologist. He is most famous for his germ theory, which showed that most infections were due to microorganisms, and for the process of pasteurization, which uses heat and pressure to prevent the spoiling of food. In fact, he was one of the founders of the modern science of microbiology, which focuses on the biology of microorganisms.
Later in his career, Pasteur studied rabies, a lethal disease that even in the twenty-first century has no known cure. His studies showed that the microorganism that causes rabies, later known to be a virus, sequestered in the central nervous system. He then used the spinal cord of a rabid dog to induce the illness in other animals. Over time, he was able to weaken the virus, with the goal of using the attenuated virus as a vaccine.
In July 1885, Pasteur was able to test his vaccine on a human being. A young man named Joseph Meister had been bitten by a rabid dog and was sure to die. Pasteur was able to treat him with his attenuated virus and saved his life. Over the subsequent years, Pasteur’s treatment saved the lives of thousands of others.