532 STUDIES ON FERMENTATION. 



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 con- 

 tained any sugar. We found that it contained less than 

 two grammes, so that 198 grammes (42 oz. Troy) had already 

 disappeared. Some time afterwards 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 medium for its nutrition, permitted the 

 perfect completion of fermentation. There was not the minutest 

 quantity of sugar remaining. The total weight of ferment, 

 after washing and drying at 100° C. (212' F.), was 2-56;3 

 grammes (39 'O grains). 



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

 be weighed, it is better not to use any j'east-ash that cannot be 

 dissolved completely, so as to be capable of easy separation 

 from the ferment formed. Kaulin's liquid, the composition of 

 which we have already given (p. 89, footnote), 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 arrested 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 found that whilst saccliaro- 

 myces jjastorianus effected a complete fermentation of the sugar, 

 the caseous ferment did not decompose more than two-thirds, 

 and the ferment which we have designated neic " /u'gh "ferment 

 not more than one-fifth : and keeping the flasks for a longer 

 time in the oven had no cfiect in increasing the proportions of 

 sugar fermented in these two last cases. 



We conducted a great number of fermentations in mineral 



