The micro-organisms of fermentation practically considered / by Alfred Jörgensen.

  • Jörgensen, Alfred, 1848-1925.
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: The micro-organisms of fermentation practically considered / by Alfred Jörgensen. Source: Wellcome Collection.

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    aside for a shorter or longer time—up to six weeks—and examined microscopically. In these investigations Hansen often found tliat tlie wort was preserved bright and apparently unchanged, even altliougli a growth had taken place. Tlierefore it is not possible to rely on tbe examination with the naked eye alone. He names tbe following as forms wbich, when tliey are present in a feeble state of growtli, cannot be detected macroscopically :—Asper- gilhts, Mucor, Penicillkim, Gladosporkim, Mycoclerma aceti and Paste^^rian^Wl, and, finally, Saccharomyces Mycoderma. Even wben these micro-organisms have fonned vigorous growths, the above-mentioned nutritive liquid has remained bright. It was further shown that Hansen, by the use of these flasks, often obtained pure cultures, since only one species was drawn into the flask with the air. It happened very seldom that three or four species penetrated into the same flask. This arises from the fact that only a very small volume of air enters each flask. The advantages of this are e\üdent, because a true knowledge of these germs can only be obtained when they have developed. In cases where several germs penetrate into the same flask, the strongest germ by its growth will, in all probability, prevent the development of the others, so that these will not be detected by a later examination. At the same time, this advantage necessitates the opening of a large number of flasks, which makes this method of investigation cumbersome and costly. Since these flasks only teil what was present in* the air at the moment of opening, ordinary boiling flasks were also used to give supplementary Information. They were allowed to stand exposed to the air of the same locality for a longer time, in some cases as long as forty-eight hours. As a simple method, Hansen usually collects the organisms by aspirating the air through water, and then adds small quantities of the water direct, or after suitable dilution, to a series of flasks containing wort. After these preliminary remarks we will give a short restimi of Hansen’s results. He confirms the Statement, first made by Pastem’, that the D