146 MICRO-ORGANISMS AND FERMENTATION. 



could be produced by adding pure cultures to sterilised " Weiss- 

 bier " wort. On the other hand, this organism had no action 

 on hopped beer- wort or low-fermentation beers. By the addi- 

 tion of tartaric acid the beer becomes normal. Schonfeld 

 distinguished many species in long " Weissbier," and, in par- 

 ticular, found two typical kinds (P. major and minor}. The 

 optimum for the formation of slime lies between 20 and 26 C. 

 These species form a considerable amount of acid, and impart 

 to the beer a pleasant, acid- wine bouquet. In presence of larger 

 quantities of alcohol the beer does not easily turn viscid, and 

 the lactic acid present protects such beer from the disease. 



These organisms grow well, according to Schonfeld, in 

 ammoniacal yeast decoction. Schonfeld has proved that such 

 species occur in horse urine. 



In ropy Belgian beer, Van Laer found the cause of this 

 disease to be small and very thin, sporogenous rods (1-6 to 

 2*4 //. long), which were partly isolated and partly united in 

 pairs by means of a zooglcea-like substance. When added to 

 beer-wort, this first becomes turbid, and afterwards ropy. 

 Milk also turns slimy, and its lactose ferments. On beef- 

 broth gelatine these rods give concave colonies with concentric 

 rings of different colours ; streak cultures give broad, white 

 bands, with a sinuous border; stab -cultures give a white 

 stripe soon extending to the bottom of the glass ; the gelatine 

 forms fissures which become filled with the growth, while at 

 the same time a speck is formed on the surface. Experiments 

 carried out with pure cultures of this bacterium in beer-wort 

 have shown that one and the same form includes many vari- 

 eties, which have a somewhat different action on wort. They 

 are all included under the name Bacillus viscosus (I. and II.). 

 If sterilised wort is infected with this bacterium, and alcoholic 

 yeast added after the lapse of some hours, the liquid becomes 

 viscous. If the wort is 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 



