STUDIES ON FERMENTATION. 209 



a kind of mycodermic film on tlie liquid surface, or a ring 

 round the sides of the flask, on a level with the liquid. This 

 development might often be mistaken for mycoderma vini or 

 cerevmm ; in reality there is not a single cell of nujcodcrma 

 formed. If we sow a trace of the new growth in a saccharine 

 medium it will behave exactly as yeast would, budding and 

 multiplying, and setting up fermentation in the liquid. And 

 thus, in spite of its mycodermic aspect, this growth is nothing 

 but yeast, since it gives rise to true alcoholic fermentation ; but 

 it is a kind of yeast which, under the foregoing conditions, 

 lives after the manner of fungoid growths, absorbing the 

 oxygen of the air and emitting carbonic acid gas. It appears 

 on the surface of all fermented liquids, especially those which, 

 like beer, contain carbohydrates, and its quantity is the greater, 

 and its action the more rapid, in proportion as it has more 

 perfect access to the air. We have termed this yeast aerobian 

 ferment or fungoid ferment. 



It may easily be understood how this kind of production has 

 escaped notice up to the present time. The conditions of our 

 experiment were, in many respects, novel ; a saccharine liquid 

 had never before been caused to ferment by means of pure 

 yeast, absolutely free from foreign germs ; a fermented liquid 

 had not previously been exposed to contact with pure air 

 for an indefinite time. On the other hand, all ordinary fer- 

 mented liquids, when left to themselves in contact with air, are 

 a ready prey to mycoderma vini or aceti at their surface, and 

 then give rise to true fungoid growths. The appearance of 

 these organisms, which always takes place soon, has thus con- 

 stantly concealed or prevented the development of the true 

 aerobian ferments. In repeating the experiment described 

 any alcoholic ferment may be used, and each one will be found 

 to produce its own peculiar fungoid form of ferment. Another 

 point worthy of notice is that these aerobian ferments, when they 

 put forth buds in the act of fermentation, reproduce the forms 

 of the original ferment, at least apparently so. In this respect 

 they cannot be distinguished, notwithstanding the fact, sur- 



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