The Ancient Greeks made a great many contributions to medicine: they discovered medicinal herbs, and surgery techniques, and even came up with the Hippocratic oath. One of the things that would not fall into this list was the four humour theory. This was the belief that the health of the human body was dependant upon the balance of four basic substances:
Diseases and physical ailments were due to either an overabundance or a startling lack of the humour in question. If you suffered from swollen eyelids, it meant you had too much blood in your system, so it was promptly bled out of you. If you had leprosy, it meant you that didn’t have enough yellow bile, and it was dripped into your mouth until you got better.
You might understand why this theory is no longer popular.
Each of the humours was also associated with a particular temperament. Blood was sanguine, and connected with fun and spontaneity. Because if there’s one thing that’s fun, it’s lots of blood! Yellow bile was choleric, and generally associated with ambition. Phlegm was phlegmatic and tied to a calm manner, while black bile was melancholic and connected to people who wrote really bad poetry.
One of the amazing aspects about the four humour belief system is just how long it lasted. It was in widespread usage until the nineteenth century, when these mysterious things called germs were discovered. Doctors realized that if you wanted to stop the spread of disease, you simply needed to wash your hands. Slightly more pleasant than draining all of the black bile out of your body to stop that pesky cold.