Fermentation and its bearings on the phenomena of disease : a discourse delivered in the City Hall, Glasgow, October 19th 1876 : under the auspices of the Glasgow Science Lectures Association / by John Tyndall.

  • Tyndall, John, 1820-1893.
Date:
1877
Catalogue details

Licence: Public Domain Mark

Credit: Fermentation and its bearings on the phenomena of disease : a discourse delivered in the City Hall, Glasgow, October 19th 1876 : under the auspices of the Glasgow Science Lectures Association / by John Tyndall. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    of oxygen necessary to tlie production of this latter gas 1 The small quantity of atmospheric au- dissolved in the -wort and overlying it would be totally incompetent to supply the necessary oxygen. In no other way can the yeast-plant obtain the gas necessary for its respii-ation than by wench- ing it from surrounding substances in Avhich the oxygen exists, not free, but in a state of combination. It decomj^oses the sugar of the solution in which it groAvs, produces heat, breathes forth carbonic acid gas, and one of the liquid pro- ducts of the decomposition is our familiar alcohol. The act of fermentation, then, is a result of the effort of the little plant to maiiitain its respii'ation by means of combined oxygen, when its supply of free oxygen is cut off. As defined by Pasteur, fermentation is life ivithout air. But here the knowledge of that thorough investigator comes to our aid to warn us against errors which have been committed over and over again. It is not all yeast cells that can thus live without air and provoke fermentation. They must be young ceils which have caught their vegetative vigour from contact with free oxygen. But once possessed of this vigour the yeast may be transplanted into a sacchar- ine infusion absolutely purged of aii', where it will continue to live at the expense of the oxygen, carbon, and other con- stituents of the infusion. Under these new conditions its life as a 2^lant will be by no means so vigorous as when it had a supply of free oxygen, but its action as a ferment will be indefinitely greater. Does the yeast-plant stand alone in its power of provoking alcoholic fermentation % It would be singular if amid the multitude of low vegetable forms no other could be found capable of acting in a similar way. And here again Ave have occasion to marvel at that sagacity of observation among tho ancients to which we owe so vast a debt. Not only did they discover the alcoholic ferment of yeast, but they had to exer- cise a wise selection in picking it out from others, and giving it special i^rominence. Place an old boot in a moist place, or expose common paste or a pot of jam to the air; it soon becomes coated Avith a blue-green mould, Avliich is nothing else than the fructification of a little plant called renicilUuin (jlaucum. Do not imagine that the mould has sprung spon-