The humoral theory presupposes the presence of four humors – Dam (blood), Balgham (phlegm), Safra (yellow bile) and Sauda (black bile) – in the body. The temperaments of persons are expressed by the words sanguine, phlegmatic, choleric and melancholic according to the preponderance in them of the respective humors – blood, phlegm, yellow bile and black bile, respectively. The humors themselves are assigned temperaments – blood is hot and moist, phlegm cold and moist, yellow bile hot and dry, and black bile cold and dry. Every person is supposed to have a unique humoral constitution, which represents his healthy state. And to maintain the correct humoral balance there is a power of selfpreservation or adjustment called Quwwat-e-Mudabbira (medicatrix naturae) in the body. If this power weakens, imbalance in the humoral composition is bound to occur. And this causes disease. In Unani Medicine, great reliance is placed on this power. The medicines used in this system, in fact, help the body regain this power to an optimum level and thereby restore humoral balance, thus retaining health. Also, correct diet and digestion are considered to maintain humoral balance.