390 JAMES M. SHERMAN 



a period of many discouragements due to lack of facilities and 

 frequent changes in the experimenting staff. 



Acknowledgment is also due to Mr, K. J. Matheson, and his 

 several collaborators, whose cordial cooperation in conducting 

 the cheese-manufacturing tests has made this work possible. 



SUMMARY 



1. Bacteria capable of fermenting lactates with the production 

 of volatile acids have been found to be constantly present in 

 normal cheese of the Swiss or Emmental type in numbers exceed- 

 ing 1,000,000 per gram. 



The discrepancies in the results of previous workers on this 

 subject are probably explained by a faulty combination of 

 salts contained in the medium used, resulting in the production 

 of a reaction too acid for the optimum development of the 

 organisms concerned. 



2. The essential organism for the production of eyes and 

 the characteristic sweetish flavor of Swiss cheese has been iso- 

 lated and studied. 



The organism concerned belongs to the group of propionic 

 acid-producing bacteria, but appears to differ slightly in some 

 of its characters from the several varieties of propionic bacteria 

 which have been described in the Uterature. 



Factory experiments have shown that pure cultures of the 

 organism may be used successfully in practice to insure the 

 proper ripening of Emmental cheese. 



