60 STUDIES ON FERMENTATION. 



the fermentation of must could not commence without the help 

 of oxygen.* 



Under the conditions of his experiment nothing could be 

 truer, and we must admire the diffidence with which this great 

 natural philosopher interpreted the fact that he had observed. 

 Another French natural philosopher, however, M. Cagniard- 

 Latour, observed that the ferment of alcoholic fermentation was 

 a little cellular plant. What was its origin in Gay-Lussac's 

 experiment? 



The advocates of the doctrine of spontaneous generation were 

 ready with their explanation, and we have seen how MM. 

 Trecul and Fremy, following many others, did not hesitate to 

 maintain that the little plant with all its particles was produced 

 by the action of oxygen on the albuminous substances contained 

 in the juice of the grapes. The experiments, which we have 

 given in the preceding paragraph, show us positively that 

 germs of the ferment of must exist on the surface of the grape, 

 and that, consequently, Gay-Lussac's experiment has a more 

 simple and natural explanation. The germs of the ferment 

 existing on the surface of the grape become mixed with the 

 juice of the grape when the latter is crushed ; these germs 

 remain inactive in the presence of hydrogen ; they vegetate as 

 soon as oxygen is introduced to them. 



Moreover, the results of our labours in connection with 

 spontaneous generation, in 1862, teach us that in Gay-Lussac's 

 experiment the germ of the ferment might also have had its 

 origin either in certain particles of dust adhering to the sides of 

 the glass bell, or upon the mercury ; and, in a laboratory 

 where alcoholic fermentation is studied, dust invariably 

 contains dry cells of ferment. The necessity of oxygen for the 

 success of the experiment is surprising, when we reflect that 



* Gay-Lussac, Annales de Cliimie, t. Ixxvi. p. 245 ; read at the 

 Institute, December 3rd, 1810. Tjong before Gay-Lussac, it had been 

 remarked that atmospheric air had a great iutluenco on fermentation. 

 See M. Chevroul's articles on the historj' of chemistry in the Journal des 

 Savants. 



