Liebig and Pasteur were in agreement on the point that fermentation is intimately connected with the presence of yeast in the fermenting liquid, but their explanations concerning the mechanism of fermentation were quite opposed.
In 1879 C. Nageli formulated his well-known molecularphysical theory, which supported Liebig's chemical theory on the one hand and Pasteur's physiological hypothesis on the other: "Fermentation is the transference of the condition of motion of the molecules, atomic groups and atoms of the various compounds constituting the living plasma, to the fermenting material, in consequence of which equilibrium in the molecules of the latter is destroyed, the result being their disintegration."
This method obtains when yeast is vigorously fermenting a saccharine solution.
In some of the true Ascomycetes, such as Penicillium glaucum, the conidia if grown in saccharine solutions, which they have the power of fermenting, develop single cell yeast-like forms, and do not - at any rate for a time - produce again the characteristic branching mycelium.
He determined the percentages of carbon, hydrogen and oxygen in the sugar and in the products of fermentation, and concluded that sugar in fermenting breaks up into alcohol, carbonic acid and acetic acid.
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