202 STUDIES ON FERMENTATION. 



as a clotted sediment, and the supernatant liquid appears 

 scarcely at all charged with globules in suspension. Again, 

 when placed on a microscope slide and compressed by the 

 cover-glass, it returns to its original form on removal of the 

 pressure. It is from these considerations that we have given 

 to it the name of caseous ferment* Lastly, this ferment pro- 

 duces a beer of a peculiar kind, which cannot be confounded 

 with other kinds of beer known in the present day. We should 

 add that it preserves its characteristics in repeated growths, and 

 that we have never found it reproduce ordinary "high " yeast. 

 When caseous ferment is sown in a saccharine medium 

 charged with mineral salts, its aspect, form, and mode of 

 budding differ completely from what they are when the ferment 

 exists in a natural medium, such as wort or other liquid adapted 

 to the nutrition and life of ferments. 



^ 



% §^ 



^8 : 4 



8 ^ 

 8 ^ 



9 S5^ 



O 



Fig. 46. 



Fig. 46 represents this ferment in course of development, 

 forty-eight hours after it had been sown in a saline medium 

 (we employed Raulin's fluid, substituting bi-tartrate for the 



* [M. Pasteur has evidently employed the word " caseous " to express 

 the curdy nature of the ferment ho is describing, its plasticity and other 

 peculiarities of physical character; but we are, nevertheless, tempted to 

 suggest that he may have had in mind also the peculiar " cheesy " odour 

 given off by these very yeasts, which he refers to in the text as containing 

 a cousidoruble intermixture of " caseous ferment." — F. F.] 



