Why doctors wore beaked masks

The mask you picture when you hear "plague doctor" is simple: a leather hood, two glass eyepieces, and a long hollow nose, about a palm's length long. It was stuffed with dried flowers, mint, cloves, and camphor; sometimes a sponge soaked in vinegar was added. The doctor breathed through a pair of holes and smelled nothing but that sharp scent the whole time.

The idea wasn't filtration, but displacement. Germs would not be discovered for more than 2 centuries, and the leading theory was miasma: disease was thought to be a property of spoiled air. Air goes bad - it stinks, so the stench must be the contagion. The conclusion, strange to us and obvious to them: if you overpower a bad smell with a strong good one, a barrier will appear between you and disease.

The rest of the outfit followed the same idea: a long waxed coat, gloves, boots, a hat, and a cane for examining patients and lifting their clothes without touching them by hand.

Plague did not end with the Black Death. It returned in waves for another 3 centuries, and cities had time to build a bureaucracy around it: quarantines, death lists, hired doctors brought in for an outbreak and sent into infected homes. Someone contracted to visit those homes every day needed protective clothing - and it appeared. Tradition credits the detailed description of the outfit to Charles de Lorme, physician to the French court.

Then comes the awkward part. The herbs in the beak did nothing: miasmas did not exist. But the waxed leather, gloves, and boots probably worked - bubonic plague is carried by fleas, and it is harder for them to bite a covered body. With the pneumonic form, which spreads through droplets from coughing, the covered face shield may have mattered too. This is a plausible reconstruction, not a measurement: no one compared groups then, and doctors in beaks still often died.