I was recently reading a book on the life of Beethoven, the composer, and what caught my attention was that he almost lost his life when doctors of the time recommended his deafness be cured by bloodletting! Apparently Mozart, Charles II, and many others were not so lucky. Even George Washington was “bled” until he died – supposedly as a cure for throat infection.
Bloodletting was a common medical practice for thousands of years until the 18th century for all types of ailments (here). Today, the technique is still used for some diseases, typically those related to an excess of iron in the red blood cells (the technique is called phlebotomy, and the diseases for which it is currently used are hemochromatosis, polycythemia, and porphyria cutanea tarda – I am not a doctor of medicine so you will have to look this up). So yes, bloodletting does make some sense for specific maladies. But to use it as a solution to everything, due to lack of understanding of biological mechanisms seems outright crazy in retrospect. But we cannot read history backwards. Given what the doctors knew at the time, and given what the principles of medicine were based on (the four elements: earth, wind, water, fire), it was the optimal, perhaps the only, solution known to the doctors of the day.
The full note on this important topic can be downloaded at this link: LTA Thinking – Bloodletting and Central Bank Pseudoscience