Many physicians believed that epidemics stemmed from the six evils: wind, cold, summer heat, dampness, dryness, and fire.
They thought epidemics arose when the weather in a given season defied its usual pattern. For example, a surviving fragment of the Treatise on Cold Damage recorded: "In spring, it should be warm, yet the cold turns bitter; in summer, it should be hot, yet the heat turns mild; in autumn, it should be cool, yet the heat turns fierce; in winter, it should be cold, yet the weather turns warm." Such conditions gave rise to "plagues."
But a fragment she had happened upon said otherwise.
Its author believed that cold, heat, warmth, and coolness were all ordinary features of the four seasons. The weather could affect them and cause them to change, but the resulting illnesses were nowhere near the same order of magnitude as a "plague." They were neither as terrifying nor as unusual.
There had to be another culprit behind a "plague"!
That was pestilential qi!
When pestilential qi struck, it felled everyone, young and old, men and women alike. The author therefore surmised that pestilential qi entered the body through the mouth and nose.
By that reasoning, if people could block their mouths and noses, they could reduce the threat pestilential qi posed to them! Masks made from kudzu linen, covering the mouth and nose to prevent patients' foul breath from entering healthy people's bodies—the core of this method of preventing disease matched the fragment's description perfectly!
In truth, some physicians already covered their mouths and noses with handkerchiefs when making house calls. But they did it not to avoid foul breath or pestilential qi, but simply because some patients' illnesses made their bodies reek. Covering their noses helped lessen the irritation.
Elder Physician Dong silently made a