Salerno's medieval treatments, and hence medical botany studies, are based primarily on the "four doctrine of humor", which in turn is based on the old "element theory". It is with Pythagoras of Samos and his followers from the Crotonian school that the doctrine associated with the concept of "harmony" that governs and governs the composition of matter is perfect in the middle of the sixth century BC. Harmony is not constant but finds itself in a constant unstable equilibrium, as a result of the balanced hostility of opposing forces inherent in things. The harmony that supports the universe supports man, gives him health, and disturbance of this balance causes disease. But Pythagoras' influence on medicine goes even further. For them, life consists of four elements: earth, air, fire and water, which correspond to four qualities: dry, cold, hot and humid. Humor (blood, black bile, bile and phlegm) corresponds to the four elements (air, earth, fire and water) and possess the same characteristics. The mood and, therefore, the elements are directly related to the so-called "initial qualities" they possess: hot, cold, wet, dry. There are four moods in the body: blood, phlegm, yellow bile and black bile. Blood is wet and warm, cold and wet sputum, yellow bile warm and dry, bile black dry and cold. A combination of these four moods determines an individual's "mood", mental qualities and state of health. It is a humor theory, which from 500 BC will dominate almost without challenge until the Virchow revolution in 1858!