|Blood||spring||air||liver||warm & moist||sanguine|
|Phlegm||winter||water||brain/lungs||cold & moist||phlegmatic|
|Yellow bile||summer||fire||gall bladder||warm & dry||choleric|
|Black bile||autumn||earth||spleen||cold & dry||melancholic|
It is believed that Hippocrates was the one who applied this idea to medicine. Humouralism as a medical theory retained its popularity for centuries largely through the influence of the writings of Galen (131-201). While Galen thought that humours were formed in the body, rather than ingested, he believed that different foods had varying potential to be acted upon the body to produce different humours. Warm foods, for example, tended to produce yellow bile, while cold foods tended to produce phlegm. Seasons of the year, periods of life, geographic regions and occupations also influenced the nature of the humours formed.
The imbalance of humours, or "dyscrasia", was thought to be the direct cause of all diseases. Health was associated with a balance the humours, or eucrasia.The qualities of the humours, in turn, influenced the nature of the diseases they caused. Yellow bile caused warm diseases and phlegm caused cold diseases.
In On the Temperaments Galen further emphasized the importance of the qualities. An ideal temperament involved a balanced mixture of the four qualities. Galen identified four temperaments in which one of the qualities, warm, cold, moist and dry, predominated and four more in which a combination of two, warm and moist, warm and dry, cold and dry and cold and moist, dominated. These last four, named for the humours with which they were associated-- that is, sanguine, choleric, melancholic and phlegmatic, eventually became better known than the others. While the term "temperament" came to refer just to psychological dispositions, Galen used it to refer to bodily dispositions, which determined a person's susceptibility towards particular diseases as well as behavioral and emotional inclinations.
Methods of treatment like blood letting, emetics and purges were aimed at expelling a harmful surplus of a humour.
Although completely refuted by modern science the theory formed basis of thinking about causes of health problems for more than a thousand years. It was seriously challenged only just before the 17th century.
There is still a remnant of the theory of the four humours in the current medical language, we refer to humoral immunity or humoral regulation to mean substances like hormones and antibodies that are circulated throughout the body.
The theory was a modest advance over the previous views on human health that tried to explain in terms of the divine. Since then practitioners started to look for natural causes of disease and to provide natural treatments.
The Unani school of Indian medicine, still apparently practiced in India, is very similar to Galenic medicine in the emphasis on the four humors and in the treatments based on controlling intake, general environment the use of purging as a way of relieving humoral imbalances.