The Semmelweis reflex or "Semmelweis effect" is a metaphor for the reflex-like tendency to reject new evidence or new knowledge because it contradicts established norms, beliefs, or paradigms. The term derives from the name of a Hungarian physician, Ignaz Semmelweis, who discovered in 1847 that childbed fever mortality rates fell ten-fold when doctors disinfected their hands with a chlorine solution before moving from one patient to another, or, most particularly, after an autopsy. (At one of the two maternity wards at the university hospital where Semmelweis worked, physicians performed autopsies on every deceased patient.) Semmelweis's procedure saved many lives by stopping the ongoing contamination of patients (mostly pregnant women) with what he termed "cadaverous particles", twenty ye