78 



Profs. H. Marshall Ward and J. Eeynolds Green. 



The differences may he important in various degrees. Leuconostoc 

 appears smaller and shorter, and withstands high temperatures ; it 

 succeeds well in grape-sugar ; its characters on gelatine media appear 

 to he different ; it can he cultivated in milk, and it forms lactic acid 

 in sugar solutions. 



How far the differences can he insisted upon cannot be determined 

 until hoth organisms have been tested side by side. 



There is one further observation to be made in support of our con- 

 tention that the viscosity depends on the deliquescence of the swollen 

 cell-walls. On agar media, which exude water, the growths are slimy 

 rather than gelatinous, and the longer the gelatine cultures are kept, 

 provided they are not allowed to evaporate, the more diffluent the 

 gelatinous lumps become. In liquid cultures, moreover, the gelatinous 

 clot does not spread evenly through the liquid, but remains around 

 the motionless organism. 



Mixed Cultures. 



Several attempts were made to obtain the typical clumps of the 

 compound organism by infecting tubes of yeast extract and saccharon 

 and other media with both the bacterium and the yeast separately 

 cultivated pme. The success was only partial, however, though it was 

 not difficult to obtain a viscous clot at the bottom of the tubes in 

 which both bacteria and yeast were embedded, the typical stiff jelly 

 clumps floating in the liquid were not formed, and here again we 

 must conclude that some definite proportion of each is necessary. 



On the Chemical Changes incident to the Fermentations. 



The jelly-like masses of which the organism consisted set up a very 

 vigorous fermentation in beer wort and in solutions of various sugars. 

 Careful cultures showed, as already stated, that the jelly was composed 

 essentially of a bacterium associated with a yeast, and a long series of 

 our experiments has been directed towards ascertaining what part 

 each played in the fermentation, and how far they assisted or impeded 

 each other. 



In the greater number of these experiments five flasks were used, 

 each of about 250 c.c. capacity. 150 c.c. of the culture fluid were 

 placed in each, and four of them were sown with pme cultures : (a) of 

 the yeast alone ; (/3) of the bacterium alone ; (7) of the yeast and the 

 bacterium separately; (8) of the two in their ordinary condition of 

 association, forming a lump of the jelly. The fourth flask contained 

 only the culture-fluid with no organism of either land. 



The culture-fluids were usually a 10 per cent, solution of some par- 

 ticular sugar to which 10 per cent, of its volume of yeast-water had 



