The Four Humors come from Hippocrates' theory that the health of a person, both mental and physical, is governed by a combination of fluids in the body: blood, yellow bile, phlegm, and black bile (yuck!). When the fluids are in balance, the ancient Greek postulated, the body and mind are in balance. Should a fluid come to predominate, the following would occur:
I. Cholericus--Too much choler, or yellow bile. This person would act angry, violent and vengeful.
II Melancholicus--The person with too much black bile would be gloomy and sad.
III. Flematicus--With too much phlegm, one was cold, emotionless (and probably in need of a tissue).
IV. Sanguinicus--An over-abundance of blood wrought cheerfulness and optimism.