Louis Pasteurs method for zapping the germs from fresh milk changed the way people bought and consumed dairy, and today many more food products are pasteurized for safety. Pasteurs work was one of the most immediate consequences of germ theory, where he worked to kill something invisible to the naked eye that nonetheless could cause grave illness.

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Medical Musings: Scientist ushered in science of immunology, ability to produce vaccines with landmark 1885 treatment - Daily Press