XXII.—The Metabolism of the Frog's Isolated Heart

Theories regarding the chemistry of the contraction process in striped muscle have been revolutionised during the last year. The Hill-Meyerhof theory was based on the assumption that the contraction process was due to the liberation of lactic acid by the break-down of glycogen, a non-oxidative reaction, and that the recovery process consisted in the oxidation of part of the lactic acid and the resynthesis of glycogen from the remainder. Meyerhof now believes (1, p. 305) that contraction is produced by the break-down of creatin-phosphoric acid (phosphagen), and that the energy produced by carbohydrate break-down is utilised to resynthesise phosphagen.