“The Four Humors”
Watercolor on Upo Paper

The Definition of the Four Humors as taken from the world’s source of Most Accurate Information, Wikipedia:

“Essentially, this theory holds that the human body is filled with four basic substances, called humors, which are in balance when a person is healthy. All diseases and disabilities supposedly resulted from an excess or deficit of one of these four humors. These deficits were thought to be caused by vapors inhaled or absorbed by the body. The four humors are black bile, yellow bile, phlegm, and blood. These terms only partly correspond to the modern medical terminology, in which there is no distinction between black and yellow bile, and in which phlegm has a very different meaning. These “humors” may have their roots in the appearance of a blood sedimentation test made in open air, which exhibits a dark clot at the bottom (“black bile”), a layer of unclotted erythrocytes (“blood”), a layer of white blood cells (“phlegm”) and a layer of clear yellow serum (“yellow bile”). It was believed that these were the basic substances from which all liquids in the body were made.

Greeks and Romans, and the later Muslim and Western European medical establishments that adopted and adapted classical medical philosophy, believed that each of these humors would wax and wane in the body, depending on diet and activity. When a patient was suffering from a surplus or imbalance of one of these four fluids, then said patient’s personality and or physical health could be negatively affected. This theory was closely related to the theory of the four elements: earth, fire, water and air; earth predominantly present in the black bile, fire in the yellow bile, water in the phlegm, and all four elements present in the blood.

Paired qualities were associated with each humor and its season. The word humor is a translation of Greek χυμός, chymos (literally juice or sap, metaphorically flavor). At around the same time, ancient Indian Ayurveda medicine had developed a theory of three humors, which they linked with the five Hindu elements.

The following table shows the four humors with their corresponding elements, seasons, sites of formation, and resulting temperaments alongside their modern equivalents.