Hippocrates (460–377 BC) postulated that the imbalance or excess of four fluids (called
humors) within the body play a role in ones emotional and physical state. The chart below shows the four humors (row 1), the condition created by too much of each (row 2), and their respective emotions (row 3):
The Hippocratic theory of personality popularized the practice of
bloodletting — opening a vein or applying leeches to "drain off" excessive amounts of the troublesome humor. In medieval Europe, it was common for barber-surgeons (whose professional practice relied on sharp instruments like knives and razors) to advertise their bloodletting services by posting a sign depicting a pale human arm traced with a crimson spiral of blood. (Remember that a largely illiterate culture required signs with pictures rather than words.) The lasting legacy of the bloodletters is the modern barber pole, a highly stylized version of the white arm with the bloody red stripe, advertising the services within. Some historian argue that Hippocrates’ four humors theory may even be the oldest constitutional theory of personality.
