Humors, Theory of

Humors are bodily fluids that according to some ancient physicians presided over illness and health. The excess of any one of the humors would lead to specific diseases, as a good balance was the condition of health. The theory of humors, which was central in medical theory for centuries, is now completely banished from the field of medicine, even if it is still part of the heritage of some alternative medicines.

The first medical references to humors are found in the Hippocratic corpus:

These were to become the canonical four humors, but even the Hippocratic corpus contains variations. For instance, the treatise Diseases IV lists phlegm, blood, bile, and water ([Hippocrates], Diseases IV, 32).

The text Nature of Man not only names the humors but also links them with the four seasons and with the mixtures of the qualities warm, cold, dry, and humid. Although the humors are always present in the body and are necessary to life, they are found in greater quantities according to the times of the year: phlegm in the winter, blood in the spring, yellow bile in the summer, and black bile in the autumn. The predominance of one humor is connected with a similarity between the humor and the season. For instance, the increase of phlegm in the winter is related to the fact that phlegm is the coldest humor. Daily occupations, the way you live, and food influence the quantity of the humors in the body: Dark wines, lentils, snails, and the meat of bulls and goats are all prone to produce black bile. Humors are natural and necessary to life, but their mixture needs to be in a state of balance toward one another. An increase in the amount of one humor or in the concentration of one humor in one place can cause diseases, such as hemorrhoids, anthrax, and cancer in the case of black bile. The cures to such imbalances are found in purgation and bloodletting.

The names of the four humors and the theory of humors were to become prevalent because they were attached to the name of Hippocrates and because they were adopted and developed by Galen, the secondcentury AD physician, who was to become central both in occidental and Arabic medicine. Yet there were competing theories. Praxagoras of Cos, for instance, was able to distinguish 11 humors. On the other hand, Erasistratus of Iulis did not reject the theory of humors, but showed caution, and was bitterly reproached by Galen for this reason. Asclepiades of Bithynia and the Methodists, a medical school that became popular in Rome, rejected the explanation of humors as a cause of diseases.

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