Writer's Almanac, Dec. 27, 2015

It's the birthday of chemist Louis Pasteur, born in Dole, France (1822). Although he was not a physician, Pasteur was one of the most important medical scientists of the 19th century. He made four important discoveries that changed the modern world. First, he discovered that most infectious diseases are caused by germs, and that instituting sanitary conditions in hospitals could save many lives. Second, he discovered that weakened forms of a germ or microbe could be used as a vaccine to immunize against more virulent forms of the microbe. Third, he discovered that rabies was transmitted by particles so small they could not be seen under a microscope, thus revealing the existence of viruses. And fourth, he developed pasteurization, a process that uses heat to destroy harmful microbes in food products without destroying the food itself.