We don’t need to wrestle with our beliefs to look at this image of a man undergoing bloodletting (about 1675) to know that this medical practice seems like a bad idea. Sure, the Ancient Greeks might have thought it could cure illnesses, but they had a totally incorrect idea that sickness originated in an imbalance of bodily fluids called humors. And we all know this idea was whacked. (#notjudginganachrinistically).
But why did bloodletting go on so long, and why was it so hard to get scientists to change their minds on this? It isn’t as though there hadn’t been observable negative bloodlettings, after all. King Charles II of England (d 1685) had a seizure at age 55, and afterwards he was bled from his jugular veins, his left arm, and through other cupping methods. He died soon after. And George Washington came down with a fever and respiratory problems in 1799, and his three physicians dutifully bled him and gave him laxatives. He passed away the next evening.
But it is very difficult to change one’s mind. The ever-insightful, if depressing, Niccolo Machiavelli wrote about “the incredulity of men, who do not readily believe in new things until they have had a long experience of them.” How can we fight our natural inclination to stick to past medical practices? Two European men from Early Modern Europe offered solutions.
The first was a mathematician called Thomas Bayes. In the mid 1700s he worked on theorems that gave rise to a way of analysing statistics to most helpfully predict correct knowledge. Called “Bayesian Interference,” the idea is to update one’s hypothesis as more evidence becomes available. Without direct reference to Bayesian ideas, Dr. Pierre Louis (d 1872) practiced another way to correctly identify harmful patterns — and this was by analyzing experimental data. In Louis’ case, he looked at 77 patients suffering from pneumonia and compared the various bloodlettings each had received. With updated information, Louis was able to surmise that bloodletting was less than efficacious.
Bayes and Louis’ ideas illustrate the importance of the scientific method in public health. Excepting rare conditions, physicians no longer practice bloodletting.
Source(s): _BCMJ_, “The History if Bloodletting,” vol 52, no 1, Jan/Feb 2010, pp 12-14, Gerry Greenstone. _National Geographic_, “Bloodletting is still happening, despite centuries of harm,” by Erika Engelhaupt, Oct 27, 2015. Image from National Geographic article via WELCOME LIBRARY. Wikipedia Bayesian interference and Bayesian statistics. YouTube, Veritasium, “The Bayesian Trap.”
