Flawed concepts with the humoral theory were accepted largely without question over thousands of years by both the masses and some of the world’s greatest thinkers.
The publication of ’De Humani Corporis Fabrica‘ by Andreas Vesalius in 1543 first brought some of the basic principles of the humeral theory into question.
But it was not until 1628 that the rot started in the form of William Harvey’s ‘De Motu Cordis‘.
This showed that blood was propelled by the heart around the body through arteries and veins and that we were in effect a biological hydraulic system.
His proposal was actively resisted although it was of course impossible to refute. However, society did not easily surrender a theory it had so firmly embraced and for nearly three centuries more, treatments based on purging, emesis, vesiculation and blood letting continued unabated.