This somewhat complex idea, whilst including, as did Liebig's theory, Stahl's fundamental conception of a transmission of a state of motion, satisfies Pasteur's contention that fermentation cannot occur without life, and at the same time explains the specific action of different organisms by differences in the constitution of their cell contents. The really essential part of Nägeli's theory consisted in the limitation of the power of transference of molecular motion to the living plasma, by which the failure of all attempts to separate the power of fermentation from the living cell was explained. This was the special phenomenon which required explanation; to account for this the theory was devised, and when this was experimentally disproved, the theory lost all significance. For nearly twenty years no further progress was made, and then in 1897 the question which had aroused so much discussion and conjecture, and had given rise to so much experimental work, was finally answered by Eduard Buchner, who succeeded in preparing from yeast a liquid which, in the complete absence of cells, was capable of effecting the resolution of sugar into carbon dioxide and alcohol [1897, 1]. In the light of this discovery the contribution to the truth made by each of the great protagonists in the prolonged discussion on the problem of alcoholic fermentation can be discerned with some degree of clearness. Liebig's main contention that fermentation was essentially a chemical act was correct, although his explanation of the nature of this act was inaccurate. Pasteur, in so far as he considered the act of fermentation as indissolubly connected with the life of the organism, was shown to be in error, but the function of the organism has only been restricted by a single stage, the active enzyme of alcoholic fermentation has so far only been observed as the product of the living cell. Nearest of all to the truth was Traube, who in 1858 enunciated the theorem, which was only proved for alcoholic fermentation in 1897, that all fermentations produced by living organisms are due to ferments secreted by the cells.