AIR AND WATER FOR MICRO-ORGANISMS. 125 



the soil and in water, they are either unable to develop in the 

 above nutrient gelatines, or they give at most only a feeble 

 growth, whilst similar germs present in the same samples give 

 a vigorous growth when sown in the flasks containing wort. 

 This will also, in all probability, hold good for several other 

 species besides those investigated. 



It was shown above that I cc. of a sample of water 

 yielded 1 500 growths by Koch's plate culture, whilst scarcely 

 ten growths were obtained when the flasks of wort were 

 employed instead of the gelatine. Although the technical 

 brewery method gives comparatively very low results, the 

 latter are also still too high. I will explain this more in 

 detail. Thus the bacteria which develop in the flasks are 

 cultivated under especially favourable conditions, and are 

 removed from the retarding influence of competing organisms ; 

 if they had been introduced into some fermenting wort taken 

 from a fermenting vessel in the brewery, a large number 

 would have been suppressed. In my experiments with Torula 

 and other species of alcoholic ferments, I have often found 

 that species which when present alone in the wort produced 

 beer of a very disagreeable flavour, were quite harmless under 

 the practical conditions of a brewery, owing to the fact that 

 when they have to compete with a good brewery yeast they 

 become completely suppressed. Nevertheless, since the 

 numbers obtained are low, ^the error which is introduced 

 through counting these latter organisms as injurious is of but 

 little moment. At all events, this holds good for the analysis 

 mentioned above. We approximate somewhat more nearly 

 to the conditions obtaining in practice when we adopt the 

 following grouping of the flasks. Those in which moulds 

 alone have developed are put aside from the rest, for these 

 are of importance only for malting. I know at least of no 

 cases in which these organisms have produced diseases in 

 beer. The remaining infected flasks are again separated 

 into two groups namely, those in which growth soon occurred, 



