BACTERIA. 75 



viscous. If the wort be infected with a mixture of absolutely 

 pure yeast and bacteria, the disease will develop in a varying 

 degree, according to the proportion of bacteria. If, however, 

 these are only added after the completion of the primary 

 fermentation, the disease will not appear at all. The greater 

 the proportion of nitrogenous matter in the liquid, the 

 sooner it will become viscous ; even liquids which do not 

 contain sugar can be made ropy by these species ; on the 

 other hand, the phenomenon does not occur in pure sugar 

 solutions. 



The so-called frog-spawn fungus (Leuconostoc mesen- 

 terioides) was investigated by Cienkowski and van Tieghem, 

 and more recently by Zopf and Liesenberg. Both the 

 European form and the variety found by Winter in Java 

 occur spontaneously in beet-root sap, and in the molasses 

 from the manufacture of sugar, in which they form large 

 slimy masses (frog-spawn) and multiply vigorously. The 

 fungus forms chains of cocci, two of which are always more 

 closely united ; in opposition to earlier observations, Zopf 

 found that these cocci present no differences with reference 

 either to their morphology or physiology ; spore formation 

 could in no case be proved. Consequently, the analogy which 

 was formerly assumed to exist between this fungus and the 

 algal genus Nostoc (implied in the name Leuconostoc) falls 

 through. 



Under certain conditions the cells become enclosed in a 

 strong gelatinous envelope, which consists of a mucilaginous 

 carbohydrate, the so-called dextran. This formation a 

 product of assimilation only occurs in the presence of grape 

 sugar, and not in solutions of milk-sugar, maltose, and dextrin, 

 because these carbohydrates and likewise glycerine cannot be 

 assimilated. Under certain conditions of cultivation, e.g., in 

 potato-cultures, the species develops quite a different form, in 

 which the gelatinous envelope is completely absent. 



The Leuconostoc ferments grape-sugar, cane-sugar (after 

 previous inversion), milk-sugar, maltose, and dextrin, with 



