124 PHYSIOLOGY OF YEASTS (Continued) 



with a decided bactericidal power. 1 The investigations of Neumayei 

 and Anderson seem to indicate that the yeasts are able to withstand 

 the action of the digestive juices and may thus pass through the di- 

 gestive canal. Hawk and his colleagues at Jefferson Medical College 

 have reported on the value of yeasts in the treatment of furunculosis. 

 They claimed better results than were secured by the use of autog- 

 enous vaccines. The use of yeasts in therapeutics is not a new idea. 

 In the earliest of times they were used against the pyogenic cocci. 



Symbiosis of Yeasts 



Symbiosis is the association of two different organisms which live 

 together, both being benefited. It seems that yeasts are able to un- 

 dergo similar associations. 



Thus it is that in certain industrial yeasts made up of differ- 

 ent fermenting agents there is a living together or a symbiosis. 2 

 Will has reported the case of two varieties of yeast which have func- 

 tioned in a brewery for 12 years without any noticeable change in 

 their individual characteristics. A sort of equilibrium seems to have 

 been established between the two varieties which permits them to 

 live together without harming each other. Schonfeld has cited a 

 similar case of a little brewery in which the leaven for four years 

 gave a rapid clarification with feeble alternation. This leaven was 

 composed of two yeasts, one which had low alternation and the other 

 with higher alternation. These two species lived for two years in 

 close contact without harm and preserved their relative strengths. 

 Van Laer has also noticed a case of equilibrium among yeasts in the 

 innoculum of a top fermentation and which for a long time lived in 

 symbiotic relations. In this, two yeasts predominated; first, a yeast 

 of the type c&revisiae which caused saccharose and maltose to fer- 

 ment; secondly, a Torula A which caused saccharose to ferment, 

 but which acted on maltose a little and which gave the beer an agree- 

 able taste and odor. Two other varieties were present to a lesser 



1 The use of yeasts in nutrition has received some attention. Voelz and 

 Baudrexel (Ann. de la Brasserie et de la Distillerie, 1911) have shown, by a 

 series of experiments with dogs, that yeasts constitute a good source of nitrogen. 

 At the suggestion of Professor Delbruck, a dozen assistants at the Fermentation 

 Institute at Berlin have replaced, for several weeks, a part of their meat at 

 breakfast by 20 gms. of dried yeast. None of them suffered any trouble by the 

 introduction of this new food (Delbruck, La Levure, un noble champignon, 1st 

 International Congress of Brewing, Brussels, 1910). Voltz (Biochem. Zeit, 93, 

 101-5) has stated that yeast should not be fed in the living condition if it is to 

 be of food value. 



2 These examples are taken from Duclaux, Traite de microbiologie, 



