Louis Pasteur was a French microbiologist and chemist who made invaluable contributions to the fields of science, industry and medicine. On this date in 1881, he first showed that sheep can be vaccinated, or protected, against anthrax, an infectious and often fatal disease that affects warm-blooded animals such as sheep and cows. He separated the bacteria that causes anthrax and vaccinated the sheep with its weakened form. In this way, Pasteur built upon the work of British physician Edward Jenner, who successfully vaccinated cows against cowpox earlier in the 19th century. In similar fashion, Pasteur also developed a rabies vaccine to protect dogs against the often-deadly virus. He learned that animals pass the virus to each other and sometimes to humans, so he also developed treatments for humans bitten by a rabid animal. Pasteur's larger theory that microbes, or germs, cause many diseases is among modern medicine's most important discoveries.

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