. Plant physiology. Plant physiology. FERMENTATION AND RESPIRATION 183 nomenon appears in the germination of seeds in darkness, where the loss in dry weight is due to respiration in the absence of the photosynthetic process. Great interest is attached to the question of the r61e of oxygen in alcoholic fermentation. Pasteur devised the apparatus shoTvn in Fig. 89 for experi- ments upon the development of yeast in the complete absence of oxygen. A fermentable liquid is placed in the flask A, which has two glass necks (o and b) with narrow openings. One of these is provided with a glass stop-cock
. Plant physiology. Plant physiology. FERMENTATION AND RESPIRATION 183 nomenon appears in the germination of seeds in darkness, where the loss in dry weight is due to respiration in the absence of the photosynthetic process. Great interest is attached to the question of the r61e of oxygen in alcoholic fermentation. Pasteur devised the apparatus shoTvn in Fig. 89 for experi- ments upon the development of yeast in the complete absence of oxygen. A fermentable liquid is placed in the flask A, which has two glass necks (o and b) with narrow openings. One of these is provided with a glass stop-cock and a glass funnel while the other bends downward into a dish (c) filled with some of the same liquid as is in the flask. Both masses of liquid are brought to boil- ing, to expel air from the hquid. After coohng, the liquid in the dish is replaced with mercury. Resting yeast cells are then introduced into the glass funnel and admitted into the flask through the stop-cock. It was found that such resting yeast cells (called "old" cells by Pasteur) produce no fer- mentation when air is entirely lacking. In another series of experiments a small amount of the fermentable Kquid was in- troduced into the funntl, in- oculated with yeast, and fer- mentation was allowed to take place. A K ttle of the ferment- ing liquid, containing a very few of the young, budding cells was then allowed to pass from the funnel into the flask, the cock being immediately re- closed. Vigorous fermenta- tion occurred in the flask, more than a gram of dry substance being obtained from the very slight amount of yeast that was introduced. It is clear, therefore, that oxygen is essential to the development of resting yeast ceUs, while young ceUs can de- velop when oxygen is entirely lacking, if nutrient materials are present. In connection with the relation of oxygen to fermentation, it is of great im- portance to discover whether normal respiration occurs in yeast abundantly supplied with oxygen. Iva
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