376 LOUIS PASTEUR 



have described, is terminated by a small piece of india-rubber 

 tube closed with a glass stopper. 



Here are the details of such an experiment: 



On December 9th, 1873, we sowed some pure ferment 

 saccharomyces pastorianus. From December n, that is, 

 within so short a time as forty-eight hours after impregna- 

 tion, we saw a multitude of extremely minute bubbles rising 

 almost continuously from the bottom, indication that at this 

 point the fermentation had commenced. On the follow- 

 ing days, several patches of froth appeared on the surface 

 of the liquid. We left the flask undisturbed in the oven, at 

 a temperature of 25 C. (77 F.) On April 24, 1874, we 

 tested some of the liquid, obtained by means of the straight 

 tube, to see if it still contained any sugar. We found that 

 it contained less than two grammes, so that 198 grammes 

 (4.2 oz. Troy) had already disappeared. Some time after- 

 wards the fermentation came to an end ; we carried on the 

 experiment, nevertheless, until April 18, 1875. 



There was no development of any organism absolutely 

 foreign to the ferment, which was itself abundant, a 

 circumstance that, added to the persistent vitality of 

 the ferment, in spite of the unsuitableness of the me- 

 dium for its nutrition, permitted the perfect completion 

 of fermentation. There was not the minutest quantity of 

 sugar remaining. The total weight of ferment, after wash- 

 ing and drying at 100 C. (212 F.), was 2.563 grammes 

 (39.5 grains). 



In experiments of this kind, in which the ferment has to 

 be weighed, it is better not to use any yeast-ash that cannot 

 be dissolved completely, so as to be capable of easy separation 

 from the ferment formed. Raulin's liquid 9 may be used in 

 such cases with success. 



All the alcoholic ferments are not capable to the same 

 extent of development by means of phosphates, ammoniacal 

 salts, and sugar. There are some whose development is ar- 

 rested a longer or shorter time before the transformation of 

 all the sugar. In a series of comparative experiments, 

 200 grammes of sugar-candy being used in each case, we 



M. Jules Raulin has published a well-known and remarkable work on 

 the discovery of the mineral medium best adapted by its composition 

 the life of certain fungoid growths; he has given a formula for the c 



to 

 com- 



