Eyelid inflammation caused by the Chlamydia trachomatis bacterium, known as trachoma. The disease is the leading cause of preventable blindness in the world today and has infected humans for millenia. CREDIT: CDC/ Susan Lindsley
Well, Galen was a 2nd century physician... Perhaps THE physician of the time, and no slouch. He was by himself in being tuned in to some of the more important medical insights of the time. Controlling infections being chief among them. He couldn’t have understood the microorganisms yet... But he developed methods that did work to reduce and prevent infections.