158 MICRO-ORGANISMS AND FERMENTATION. 



the pronounced honey odour. In sweet wort they give a 

 pleasant sourish odour and flavour. They are grouped 

 together under the name P. acedulefaciens. Other varieties have 

 been described by Schonfeld giving a red colour to lager beer. 

 By inoculating a pure culture of a species producing strong 

 turbidity into pasteurised beer which is allowed to stand, he 

 showed that in most cases only a sedimentary growth developed, 

 but if, on the contrary, carbon dioxide is passed through the 

 beer, freely swimming bacteria develop which produce turbidity. 

 This observation agrees with those made by Reichard in practice. 

 The fact that cases do occur in which lager beer 

 contains bacteria appearing to possess the characters 

 of true beer Sarcina, but having no recognisable influence 

 either on the clearness, the odour, or flavour of the liquid, has 

 .since been confirmed in the author's laboratory. Experi- 

 ments have proved that in isolated cases growths of one and 

 the same species have caused diseases in one beer and not in 

 another. From a number of individual observations of the 

 .associated conditions, the following conclusions may be 

 drawn : Species may be isolated from yeast and from lager 

 beer capable of development, which appear to be incapable of 

 exciting any disease whatsoever in the latter. The extent 

 to which such organisms occur in beer is not yet 

 known with certainty. Amongst the true disease species, a 

 given organism appears to be unable to produce the special 

 disease under all circumstances, even when the conditions are 

 favourable for the reproduction of cells. According to our 

 present experience, the most likely assumption appears to 

 be that this is caused by the condition of the liquid 

 at the time when the contamination with bacteria took place. 

 According to the published experiments, the possibility cannot, 

 therefore, be excluded that these organisms are capable of 

 variation like other bacteria, and the question arises how far 

 they are able to retain their newly- won properties. 



No proof has yet been given that foreign species can be 

 so completely acclimatised that they may act as disease 

 bacteria in lager beer. 



Both the typical Sarcina and the Micrococci (Pediococci) 

 .are widely distributed in nature, and may easily be recognised 



