PPE and pestilence: The origins of medical masks

Very interesting. It may be obvious to us now that masks can slow down the spread of airborne contagions, but before the discovery of bacteria in the 1800s, how were scientists, and the public, to know that masks saved lives? Not mentioned in the article, but after the discovery of bacteria washing one's hands, and even the wearing of gloves in surgery, became common place. The practice of washing hands probably did more to extend the human lifespan between 1800 and 1900, from 38 years to 49 years in the West, than any other single thing.