Otto Meyerhof (1884-1951) was awarded half of the 1922 Nobel Prize for Physiology or Medicine for his discovery of the relationship between the consumption of oxygen and the metabolism of lactic acid in muscle. He showed that, in frog muscle, the lactic acid formed is reconverted to carbohydrate in the presence of oxygen. Meyerhof also prepared an extract of muscle which could carry out all the steps of glycolysis with added glycogen and hexose-diphosphate in the presence of hexokinase derived from yeast. Using this system, he and his associates were able to reconstruct in vitro the main steps of the reactions leading from glycogen to lactic acid. Meyerhof introduced the term glycolysis to describe the anaerobic degradation of glycogen to lactic acid and showed the cyclic nature of energy transformations in living cells. The complete metabolic pathway of glycolysis is known as the Embden-Meyerhof pathway after Meyerhof and Gustav George Embden.