DAIRY FARMING DAIRYING. 287 



Duclaux and his followers ascribe the chief importance in the process 

 to the peptonizing bacteria in general and to the representatives of the 

 genus Tyrothrix in particular; i. e., to bacteria which liquefy gelatin. 



Freudenreich has been led to conclude that the gelatin liquefying 

 bacteria (Tyrothrices, etc.) occur in cheese and milk in but small num- 

 bers; if added to cheese in great quantities they rapidly disappear 

 except when introduced as spores. In the latter case they live in the 

 cheese considerably longer but do not multiply. Admitting tbat the 

 Tyrothrices play an important part in the ripening of cheese, it will be 

 necessary, Freudenreich contends, to assume that they exist in the curd 

 soon after coagulation and secrete a diastase which induces the ripening 

 of the cheese. But since the Tyrothrices occur in milk and cheese in 

 but limited numbers, he believes it improbable that they could secrete 

 the diastase in a quantity sufficient to transform the whole mass of the 

 cheese. While the bacteria liquefying gelatin disappear from the 

 cheese very rapidly, even when introduced artificially in very great 

 numbers, the lactic acid bacteria multiply in the cheese in enormous 

 quantities. In consideration of this, Freudenreich thinks it probable 

 tbat the lactic acid bacteria play the chief, if not the exclusive, role in 

 the ripening of at least Emmenthaler cheese; in soft cheeses, O'idium 

 lactis and some other fungi cooperate with the lactic bacteria. 



Adametz claims to have discovered a bacillus in Emmenthaler cheese 

 possessing at first the properties of peptonizing bacteria and later those 

 of a lactic ferment. 



The author took up the study of the problem in question by preparing 

 in milk pure cultures of some peptonizing bacteria as well as of lactic 

 bacteria and then investigating by means of chemical aualysis the 

 changes which took place in the milk in the course of the development 

 of the microorganisms in it. The change in the composition of the milk 

 was studied as to (1) the quantity of the casein of the milk converted 

 into a soluble form; (2) the amount of ammonia formed in the cultures, 

 and (3) the amount and kind of fatty acids produced by the micro- 

 organisms. 



With reference to the first point, it was found that while the pepton- 

 izing bacteria converted during the first 15 days of their culture almost 

 all of the casein of the milk into proteids soluble in water and the 

 remainder into products of decomposition, the lactic bacteria did not 

 alter in the slightest the amount of nitrogen in the soluble protein 

 matter after 30 days of culture. In other words, while the bacteria of 

 the former group acted very energetically on the casein, those of the 

 latter group did not affect it at all. The fungus O'idium lactis was also 

 found very active in changing the casein, although in a lesser degree 

 than the peptonizing bacteria. 



Further, the author found in the cultures of O'idium lactis less 

 ammonia than in those of the peptonizing bacteria, and none whatever 

 in the cultures of the lactic bacillus. 



