The demise of bloodletting.
Bloodletting was a practice favoured by doctors and barber-surgeons for many centuries, and is now, perhaps surprisingly, still employed for a few specific indications. The effectiveness of bloodletting for treating diseases such as pneumonia was convincingly challenged in the mid-nineteenth century, but medical conservatism ensured the practice continued well into the twentieth century. As late as 1942, a famous medical textbook considered bloodletting appropriate treatment for pneumonia.
['Thomas|D P|DP|']
D001815:Bloodletting D049670:History, 17th Century D049671:History, 18th Century D049672:History, 19th Century D049673:History, 20th Century D049690:History, Ancient D049691:History, Medieval D006801:Humans D024763:Leeching D011014:Pneumonia
Bloodletting pneumonia lancets leeches transfusion