Bloodletting

Science sometimes goes down an incorrect path. Though the path is wrong, a detailed superstructure of learning gets built on top of the incorrect premise. Such was the case with the medical practice of bloodletting in the early 1800s, where detailed procedures were developed regarding which veins to open for a given set of symptoms. One leader in this practice was America's Dr. Benjamin Rush: "Early in the [1800s], ... physicians put their faith in bloodletting, to draw out the evil humors which were believed to cause disease. With bloodletting, it took years of learning to know precisely which veins, by what rituals, were to be opened for what symptoms. A superstructure of technical complication was erected in such deadpan detail that the literature still sounds almost plausible. "However, because people, even when they are thoroughly enmeshed in descriptions of reality which are at variance with reality, are still seldom devoid of the powers of observation and independent thought, the science of bloodletting, over most of its long sway, appears usually to have been tempered with a certain amount of common sense. Or it was tempered until it reached its highest peaks of technique in, of all places, the young United States. Bloodletting went wild here. It had an enormously influential proponent in Dr. Benjamin Rush, still revered as the greatest statesman-physician of our revolutionary and federal periods, and a genius of medical administration. Dr. Rush Got Things Done. Among the things he got done, some of them good and useful, were to develop, practice, teach and spread the custom of bloodletting in cases where prudence or mercy had heretofore restrained its use. He and his students drained the blood of very young children, of consumptives, of the greatly aged, of almost anyone unfortunate enough to be sick in his realms of influence.

Bloodletting in 1860, one of only three known  photographs of the procedure.

"His extreme practices aroused the alarm and horror of European bloodletting physicians. And yet as late as 1851, a committee appointed by the State Legislature of New York solemnly defended the thoroughgoing use of bloodletting. It scathingly ridiculed and censured a physician, William Turner, who had the temerity to write a pamphlet criticizing Dr. Rush's doctrines and calling 'the practice of taking blood in diseases contrary to common sense, to general experience, to enlightened reason and to the manifest laws of the divine Providence.' Sick people needed fortifying, not draining, said Dr. Turner, and he was squelched. ... "In the pseudoscience of bloodletting ... years of learning and a plethora of subtle and complicated dogma [arose] on a foundation of nonsense."