34 THE AMERICAN MONTHLY [Feb., 



by merely counting the number of pastorian and oval 

 cells with a pale, " wild " appearance. The percentage 

 of wild forms among the cultivated ones can be ascer- 

 tained successfully only from the spore-cultures where 

 the spores allow comparison. 



When the yeast is taken from the brewery directly into 

 the laboratory and examined, it is vigorous and in good 

 development : therefore, it can be cultivated for spores 

 at once. If we have, on the other hand, a pure culture, 

 this must be ''freshened up" in beer-w^ort for 24 hours 

 before it is transferred to the gypsum. This is done in 

 the way that a trace from the original culture is brought 

 into a new flask with sterilized beer-wort and kept by 

 25°C for 24 h. 



The Freudeureich flask is the best for common use 

 (see Salomonsen's Bact. Technol., 1. c. p. 456, Fig. 10, to 

 the right), but the Chamberland flask or a common test 

 tube also work well. In extensive and important studies, 

 the Pasteur flask (latest modification) is indispensable 

 but more difficult to manipulate than other flasks. Among 

 the many media prescribed and used none is better or 

 more natural than beer-wort (gehopfteWuerze in German 

 breweries), the wort generally to be had in breweries is 

 too concentrated, and sterile water should be added 

 (from I to 1 vol. of water to 1 vol. of the wort). It must 

 be sterilized and carefully filtered until it is absolutely 

 clear and then poured into the small flasks or tubes.* 

 To these a little sterile water is added and then they are 

 again sterilized as other media. Before they are put 

 aside they are examined every day for three or four days. 

 If any vegetation appears they must be re-heated, wa- 

 ter being added in order to prevent excessive evapora- 

 tion. The laboratory must be kept closed and no win- 

 dows opened while the pure cultures are made. 



^Everything must be sterilized belore being used. See Salomonsen, 1. c. 

 p. 440. 



