160 MICRO-ORGANISMS AND FERMENTATION. 



fermented by the addition of yeast ; starch is then added, and 

 after clearing it is neutralised with ammonia, and reduced to- 

 an alcohol content of 4 per cent. The sample is mixed with 

 this liquid, and the development observed in the sealed pre- 

 paration. It will be found that of bacteria, only Sarcince 

 come to development. In the author's laboratory, for many 

 years past, an addition of neutral yeast water (preserved in 

 flasks along with an excess of calcium carbonate) is made to 

 the sample taken at the end of the principal fermentation. 

 After two days' standing the Sarcince present have multiplied 

 sufficiently to be easily recognisable under the microscope. 

 Until investigations have gone far enough to enable us to 

 prove whether the haunts of these disease germs lie outside 

 the plant, efforts must be directed in practice to finding their 

 haunts within the plant. We must bear in mind the limits of 

 our present knowledge, and we must not forget that without- 

 pure culture experiments direct observation of Sarcina-lilie 

 germs in the plant itself (for example in the vats) suggests a 

 much greater probability that these growths are dangerous in 

 practice, than if a large number of germs of similar microscopic 

 appearance had been observed, with the help of plate-cultures, 

 in the air surrounding the brewery or in the water used 

 in the plant. By means of a properly organised system of 

 disinfection, and often without the application of antiseptics, 

 such growths may be entirely suppressed. It is an entirely 

 false impression that the beer Sarcince described in this section 

 cannot be fully excluded, a mistake that has arisen because 

 it has proved impossible to distinguish between many of the 

 organisms of this large group of bacteria occurring in air and 

 the true disease species of beer. 



Investigations carried out in the author's laboratory on 

 bright wines have frequently brought to light vigorous growths 

 of Sarcina forms, and at the same time the wine has assumed 

 a peculiar odour, which resembles to a remarkable extent the 

 odour and taste of beers in which such growths occur. 



10. The Fermentation of Tobacco. 



During the fermentation which dried tobacco leaves 

 undergo, a number of organisms are present, and it is a natural 



