FERMENTS, FERMENTATIONS, AND LIFE. O54 
ferment. To ascertain this, he measured the quantity of 
sugar decomposed in a given time by a fixed weight of yeast, 
and he found —after first establishing that a cubic mil- 
limetre of yeast contains about 2,772,000 cells—that the 
power of a million of cells represents the force capable of 
decomposing four grains of sugar in an hour. If we at- 
tempted according to this estimate to express in figures the 
number of cells employed in producing the wine, beer, and 
cider, consumed every year, as JJumas says, even astrono- 
mers would shrink from the task. 
This active property of decomposing sugar, and forming 
alcohol in consequence, does not belong to the cells of 
brewer’s yeast exclusively. Several chemical agents possess 
the same power, and certain vegetable cells also are adapted 
to use it. When fruits are placed in a medium filled with 
oxygen, they absorb this gas, and occasion the release of 
carbonic acid ; if, on the contrary, they are left in carbonic 
acid or any other inert gas, they effect the production of 
alcohol. The fruits remain firm and hard, without suffer- 
ing any external change, but the sugar they contain is 
transformed in part into alcohol. How is this phenomenon 
to be explained? In common air, the cell of the fruit is fed 
by oxygen; if this gas is withheld, it is forced to borrow the 
materials of nutrition from the fluids that moisten it, that 
is, from the saccharine juice, and then the latter is decom- 
posed. Pasteur has noted that a similar alcoholic fermen- 
tation takes place in other vegetable organs, in leaves, for 
instance, and in every case he has proved that the phenom- 
enon is due to the cells of the vegetables alone, and not 
to yeast-globules. Far from throwing any doubt on the 
physiological doctrine of fermentation, these singular facts 
agree in lending it support, by giving it deeper and more 
general application. 
We have seen that the fermentation of sugar yields 
alcoho]. The latter, brought in contact with certain porous 
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