
In the second century ad, a brilliant physician had a powerful idea: 4 humours, in varied combinations, produced all illness. From that date until the late 19th century, Galen's theory ruled medicine. Its corollary was that the treatment of disease involved getting the humours back in order; releasing them through bloodletting was the most common procedure and was often augmented with other means of freeing bodily fluids (eg, purgatives and laxatives).
