Elements of human physiology / by Henry Power.

  • Henry Power
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: Elements of human physiology / by Henry Power. Source: Wellcome Collection.

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    of free oxygen, evolves carbonic acid with formation of alcohol, and it has been proved by Pasteur that this fermentation is not accompanied by the develop- ment of any microscopic organism. Closely related to this is the well-established fact that large quantities of sugar may be made to ferment by means of yeast, without the latter multiplying to any noteworthy extent. On the other hand, the makers of German barm obtain large quantities of yeast without produc- ing much alcohol. Brefeld, indeed, succeeded, by means of a peculiar artifice, in growing saccharomyces in brewers' wort without producing a trace of alcohol (Dittman). Hence it would appear that vinous fer- mentation, far from being the characteristic life func- tion of healthy saccharomyces, is dependent on a certain pathological condition of cells, normally growing in darkness, which is brought about by im- mersing them in saccharine fluids, and shutting them out from oxygen, which they need for their healthy development; and the best authorities go no farther than to admit that these living organisms are the only known sources for the ferments proper, which in themselves are chemical substances pure and simple. Many other kinds of fermentation, such as that, for instance, in which hydrated milk sugar . ,, lactic acid, are associated with the multiplication and develop- ment of a form^ed ferment, which in this case is known as the bacterium lactis, and is of extremely small size. Similar organisms are found in viscous fermentation, to which wine is liable when it becomes ropy and contains a kind of gum ; in butyric fermenta- tion, where glucose breaks up into lactic acid, butyric acid, carbon dioxide, and hydrogen gas ; and in putre- faction, which is a highly complex process.
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