Alcoholic fermentation / by Arthur Harden.

  • Arthur Harden
Date:
1932
Catalogue details

Licence: In copyright

Credit: Alcoholic fermentation / by Arthur Harden. Source: Wellcome Collection.

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    Schwann found on repetition that the results were irregular. Some- times all the flasks showed fermentation, sometimes none of them. This was correctly ascribed to the experimental difficulties, but none the less served as a point of attack for hostile and damaging criticism at the hands of Berzelius (p. 8). The origin of putrefaction was definitely attributed by Schwann to the presence of living germs in the air, and the similarity of the result obtained with yeast suggested the idea that alcoholic fermentation was also brought about by a living organism, a conception which was at once confirmed by a microscopical examination of a fermenting liquid. The phenomena observed under the microscope were similar to those noted by Cagniard-Latour, and in accordance with these observations alcoholic fermentation was attributed to the development of a living organism, the fermentative function of which was found to be destroyed by potassium arsenite but not by extract of Nux vomica, so that the organism was regarded rather as of vegetable than of animal nature. This plant received the name of “ Zuckerpilz ” or sugar fungus (which has been perpetuated in the generic term Saccharomyces). Alcoholic fermentation was explained as “ the decomposition brought about by this sugar fungus removing from the sugar and a nitrogenous substance the materials necessary for its growth and nourishment, whilst the remaining elements of these compounds, which were not taken up by the plant, combined chiefly to form alcohol.” Kiitzing’s memoir, the third of the trio [1837], a^s0 dates from 1837, and his opinions, like those of Cagniard-Latour, are founded on microscopical observations. He recognises yeast as a vegetable organism and accurately describes its appearance. Alcoholic fermen- tation depends on the formation of yeast, which is produced when the necessary elements and the proper conditions are present and then propagates itself. The action on the liquid thus increases and the constituents not required to form the organism combine to form un- organised substances, the carbonic acid and alcohol. “ It is obvious,” says Kiitzing, in a passage which roused the sarcasm of Berzelius, “ that chemists must now strike yeast off the roll of chemical com- pounds, since it is not a compound but an organised body, an organism.” These three papers, which were published almost simultaneously, were received at first with incredulity. Berzelius, at that time the arbiter and dictator of the chemical world, reviewed them all in his “ Jahresbericht ” for 1839 [1839] with impartial scorn. The micro- scopical evidence was denied all value, and yeast was no more to be
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