3. Each of the four chief fluids of the body (blood, phlegm, yellow bile (choler), and black bile (melancholy)) that were thought to determine a person's physic

3. Each of the four chief fluids of the body (blood, phlegm, yellow bile (choler), and black bile (melancholy)) that were thought to determine a person's physical and mental qualities by the relative proportions in which they were present.