Four humours. Historical artwork of a half male and half female figure illustrating the four humours. The four humours are the bodily fluids: phlegm, blood, black bile and yellow bile. Imbalances in these humours were supposed to govern illness and were linked to the personality types flegmat (phlegmatic), sanguin (sanguine), melanc (melancholic) and coleric (choleric) respectively. It was thought that an imbalance of humours could be redressed by changing the patient's diet, prescribing medicine, carrying out surgery or through bleeding. This artwork is from the Book of Alchemy by Thurn-Heisser, Leipzig, Germany (1574).