SLIME-FORMING BACTERIA. 147 



can be made ropy by these species. When the nutritive liquid 

 contains much sugar, the fungus develops very feebly, and in pure 

 sugar solutions the phenomenon does not occur. A high con- 

 tent of acid greatly restricts the development of these bacteria. 

 Van Laer has since isolated a Bac. viscosus bmxellensis 

 which produces, in addition to slime, a peculiar disease called 

 *' biere a double face." It occurs in " spontaneously " fer- 

 mented Belgian beers, Lambic, Faro, and Mars, and can be 

 recognised by the fact that the beer looks clear in transmitted 

 light, and milky in reflected light. It forms a long rod making 

 a white tough film on beer-wort, which grows down into the 

 liquid. Subsequently the slime disappears, and the rods are 

 then surrounded by a slimy envelope. On Avort gelatine large, 

 round, slimy, transparent colonies are formed, with a yellow 

 centre and with many zones. The species restricts the activity 

 of alcohol yeasts, and beer attacked by it is consequently poor 

 in alcohol, and richer in extract than sound beer. It forms 

 lactic, acetic, and butyric acids. 



Vandam found in English beers an aerobic Bac. viscosus 

 (III.), which occurs as small rods, single or in chains, consisting 

 of two, three, or more links, with spore-formations in the 

 centre of the rods. This bacillus develops best at about 

 30 C., and produces a slimy mass in brewers' wort, which 

 under the microscope proves to consist of zooglcea formation. 

 After the lapse of some time the liquid has the consistency 

 of albumen. No gas is evolved, but the liquid acquires a 

 peculiar odour. On meat-juice gelatine and on wort-gelatine 

 the growth develops freely. The viscosity of the liquid does 

 not seem to depend on the quantity of nitrogenous matter 

 present, but on the other hand, the bacillus grows feebly in 

 the absence of sugar. This species is incapable of producing 

 disease in beer unless it is thriving well, and is introduced 

 in large quantities into the wort before or during pitching. 

 Like the form discovered by van Laer, it ferments milk- 

 sugar ; and, according to Vandam, it is easy to detect it in 

 yeast, even in traces, simply by introducing a sample of the 

 latter into nutritive liquid containing milk-sugar, a growth of this 

 species soon making its appearance in the upper part of the liquid. 

 Brown and Morris mention a Coccus form which also seems 



