CHEESE 367 



to the ripening process has been concerned with a deter- 

 mination of the function or part played by these various 

 groups of bacteria, and how the several kinds affect the 

 different components of cheese. The chief views held by 

 the different workers at the problem are discussed below. 

 (a) Duclaux, who was the first to make a systematic 

 study of the ripening process, isolated from Cantal cheese 

 ten species of bacteria, the most important of which were 

 placed by him in the genus Tyrothrix. The latter were 

 all somewhat large bacilli, which grew readily in milk 

 and other liquid media into large threads sometimes 

 100 //. to 1 20 & long, and formed spores which were able 

 to resist a temperature of 100 C. for a short time. 

 They are now known to be very similar in many of 

 their characters to the hay bacillus (Bs. subtilis) and the 

 potato bacillus (Bs. vulgatus}. ' When introduced into 

 milk Duclaux found they were able to decompose the 

 casein with the production of an albumose, amino-acids, 

 and other compounds met with in ripened cheese, and 

 concluded that they were the chief agents in the ripening 

 process. The power of these organisms to peptonize 

 casein Duclaux considered was due to the secretion by 

 them of a proteolytic enzyme, casease, which diffused 

 slowly throughout the substance of the cheese. Since 

 the peptonizing bacteria are checked by the presence of 

 much acid, they only begin their specific work after the 

 initial lactic .fermentation is over, and the acid produced 

 has been destroyed or neutralized. This view has been 

 supported by Adametz, Von Klecki, Winkler and others, 

 and a pure culture of Bacillus nobilis, an aerobic form of 

 a Tyrothrix obtained from Emmenthal cheese, has been 

 sold for cheesemaking under the name " tyrogen" Its 

 use, however, has not met with success. If the peptonizing 



