ACTION OF OXYGEN ON WINE 137 



sulphurous acid the casks in which it was to be received; 

 also, in some portions of the country, to fill, that is, to 

 keep constantly full, the casks in which it was stored. 

 It was said that it is more exposed to the danger of 

 spoiling in casks of permeable wood than in glass bottles. 

 It was well known that it became flat in contact with the 

 air, and recently M. Berthelot had quite justly related 

 this phenomenon to an absorption of oxygen. Bous- 

 singault had shown, on his part, that the wine of casks 

 contained only nitrogen and carbonic acid, that is to 

 say, there is no longer a trace, in the free state, of the 

 oxygen which it has certainly taken from the air at the 

 same time as the nitrogen. In short, for science as for 

 practice, wine seemed to be a substance most oxidizable 

 and unstable in regard to aeration. 



Of that there was no doubt. Pasteur had a great 

 respect for secular practices and said that science ought 

 not to condemn them lightly, but that it had always the 

 right to search for their interpretation. It might be 

 that the wine was really unable to endure contact with 

 air, but also it might be that air is necessary to the 

 microbes which menace the wine, and that to deprive 

 it of the air would, in a measure, guarantee it against 

 disease. 



Pasteur had already arrived at a stage where he could 

 accept only the second of these two interpretations. He 

 knew from his experiments on spontaneous generations, 

 how little organic substances are oxidizable without the 

 intervention of microbes, and on the other hand, he had 

 just seen that the acetic ferment which constantly 

 threatens wines with acetification has great need of oxy- 

 gen. Furthermore, while he was studying this myco- 

 derma of vinegar he had also studied another superficial 

 pellicle, that which forms so easily on the surface of 

 wine left behind in filling the bottles and which resem- 



