The "humoral theory" of disease, which originated with Hippocrates (who lived from about 460 to about 370 B.C.) and lasted until the early 20th century, held that a balance had to be maintained among four humors or liquid substances in the human body. If that balance got out of whack, the thinking was, people got sick.
The four humors were black bile, red or yellow bile, blood and phlegm. The ancients believed that these substances ruled our personalities as well as our bodies. They divided all the possible character types into these four — melancholic, choleric, sanguine and phlegmatic — depending on which substance dominated that particular person.
Treatments for disease were designed to restore the balance among the humors, but what worked for one person might not work for another, which helped let practitioners off the hook if a "cure" didn't work. Purges like enemas and emetics were popular, and physicians often advised changes to a patient's diet or routine. Blood-letting was an especially durable cure for just about anything.
During labor, for example, "some women were bled to unconsciousness to counter delivery pains" or any other complications large or small, according to Peter Conrad's The Sociology of Health and Illness.
The acceptance of the germ theory finally put an end to humoral theory in mainstream medical thought.