Doctors kept bleeding patients for two centuries after Harvey disproved the idea
For over 2,000 years, draining blood was medicine's default treatment. William Harvey undercut its theory in 1628, and by the 1830s careful counting showed it did nothing for pneumonia. Yet French doctors were still importing about 40 million leeches a year, and George Washington was bled of roughly 3.75 litres before he died.
The logic came from humoral medicine, which held that health depended on balancing four bodily fluids: blood, phlegm, black bile and yellow bile, each tied to one of the classical elements. Hints of the practice appear in ancient Egypt, where some accounts claim the idea came from watching hippos, whose reddish secretions were mistaken for blood. In Greece, Hippocrates mentioned it but preferred diet, and he saw menstruation as a way of purging women of bad humours, a model for bleeding.
Galen, working under the Roman Empire, made bloodletting central. He believed blood was produced and consumed rather than circulating, so it could pool and stagnate, and he worked out elaborate rules for how much to take according to age, season, weather and place, even pairing particular veins with particular organs. The idea spread widely. The Talmud named suitable days, medieval charts matched bleeding sites to the planets, and Islamic surgeons, following translated Greek texts, prescribed it especially for fevers, which helped push it further into Latin Europe. Ayurvedic writing described it as well.
Physicians prescribed, but barbers did the cutting, which is where the barber's red-and-white pole comes from: red for blood, white for bandages. Methods ranged from opening a forearm vein to heated glass cups and spring-loaded blades, and sessions often ran until the patient fainted, which was thought beneficial. One British text recommended it for about a hundred ailments beyond a long list that included asthma, cholera and smallpox. In 1623 the French physician Jacques Ferrand even proposed it as a cure for heartbreak.
Evidence arrived slowly and met resistance. In the 1830s Pierre Charles Alexandre Louis used numerical methods to show bleeding failed against pneumonia and fevers, but many doctors refused to trust someone else's numbers over tradition. In America, Benjamin Rush, a signer of the Declaration of Independence, urged unusually heavy bleeding. Today the old practice is regarded as pseudoscience, although drawing blood remains a real treatment for a few conditions such as haemochromatosis.
Source: Bloodletting
