[From "processing" and "fermentation" to oxidative metabolism]

The theory of the four humors or humorism (Hippocrates of Kos) viewed disease as an imbalance of the humors. Galen of Pergamon further developed the theory by describing digestion as a sequence of chemical reduction processes that convert into the various humours. Theophrastus von Hohenheim attempted to overcome humorism in the 16th century and establish medicine on a natural-philosophical-alchemical basis. The era of empirical-experimental chemically oriented medicine began with "iatrochemistry" in the 17th century. Franciscus Sylvius' concept of disease is based on an imbalance of acidic and alkaline fermentation. It was Lazarro Spallanzani who understood the digestive processes in the stomach as a chemical dissolution of food. The discovery of oxygen and the process of oxidation by Lavoisier laid the foundation for our understanding the physiology of metabolism.