FERMENTATION. 541 
important fact that all ripening fruit, exposed to the free 
atmosphere, absorbed the oxygon of the atmosphere and 
liberated an approximately equal volume of carbonic acid. 
He also found that when ripe fruits were placed in a con- 
fined atmosphere, the oxygen of the atmosphere was first 
absorbed, and an equal volume of carbonic acid given out. 
But the process did not end here. After the oxygen had 
vanished, carbonic acid, in considerable quantities, con- 
tinued to be exhaled by the fruits, which at the same time 
lost a portion of their sugar, becoming more acid to the 
taste, though the absolute quantity of acid was not 
augmented. This was an observation of capital importance, 
and Berard had the sagacity to remark that the process 
might be regarded as a kind of fermentation. 
Thus the living cells of fruits can absorb oxygen and 
breathe out carbonic acid, exactly like the living cells of 
the leaven of beer. Supposing the access of oxygen sud- 
denly cut off, will the living fruit cells as suddenly die, or 
will they continue to live as yeast lives, by extracting 
oxygen fron the saccharine juices round them? This is a 
question of supreme theoretic significance. It was 
first answered affirmatively by the able and conclusive 
experiments of Lechartier and Bellamy, and the answer 
was subsequently confirmed and explained by the experi- 
ments and the reasoning of Pasteur. Berard only showed 
the absorption of oxygen and the production of carbonic 
acid; Lechartier and Bellamy proved the production of 
alcohol, thus completing the evidence that it was a case 
of real fermentation, though the common alcoholic ferment 
was absent. So full was Pasteur of the idea that the cells 
of the fruit would continue to live at the expense of the 
sugar of the fruit, that once in his laboratory, while con- 
versing on these subjects with M. Dumas, he exclaimed, 
" I will wager that if a grape be plunged into an atmos- 
phere of carbonic acid, it will produce alcohol and carbonic 
acid by the continued life of its own cells that they will 
act for a time like the cells of the true alcoholic leaven." 
He made the experiment, and found the result to be what 
he had foreseen. He then extended the inquiry. Plac- 
ing under a bell-jar twenty-four plums, he filled the jar 
with carbonic acid gas; beside it he placed twenty-four 
similar plums uncovered. At the end of eight days he 
lemoved the plums from the jar and compared them with 
