288 EXPERIMENT STATION RECORD. 



Finally, on comparing the nature of the fatty acids formed in cheese 

 (the author experimented with the hard Gray ere and the soft Brie cheese) 

 and those produced by the bacteria in pure cultures, he found that the 

 mixture of the volatile acids caused by the bacilli not liquefying gela- 

 tin did not correspond to those which are formed either in the hard or 

 in the soft cheese. On the contrary, the volatile acids produced by the 

 peptonizing bacilli were found to be very similar to the mixture of these 

 acids produced in the ripening of the Gruyere cheese. And, lastly, 

 great similarity was observed between the volatile acids of the soft 

 Brie cheese and those produced by the fungus Oidium lactis. 



Thus all three lines of investigation pursued by the author lead to 

 the conclusion that the bacteria of lactic fermentation, though present 

 in the milk and cheese in very great numbers, do not induce the changes 

 in the casein in the process of ripening, and if they exert any influence 

 at all it is only indirect, since these bacteria do not dissolve casein, do 

 not give off ammonia, and do not form the volatile acids characteristic of 

 ripened cheese. The peptonizing bacteria and the fungus Oidium lactis, 

 on the other hand, produce all the changes of casein which take place 

 in the ripening of cheese; th y yield soluble proteids and decompose 

 albuminous compounds with the formation of ammonia and volatile 

 acids corresponding to those occurring in cheese. 



It is pointed out that the peptonizing bacteria would appear from the 

 foregoing to play an exclusive part in the ripening of cheese, but such 

 a conclusion would overlook the important fact established by the 

 analyses of Bodzinsky, namely, that there is in cheese only a small 

 quantity of peptone which is not precipitated by ammonium sulphate. 

 In opposition to this fact the author found while investigating the 

 nature of the soluble albuminous bodies in pure cultures of peptonizing 

 bacteria that, under the influence of these microorganisms, the casein 

 is converted almost entirely into peptone. In view of these opposing 

 facts the author concludes that the joint action of the peptonizing bac- 

 teria and the lactic acid bacteria must be considered as essential to the 

 ripening of cheese, and that this should serve as the starting point for 

 future investigations of the process. The lactic acid bacteria are 

 not capable of inducing this process, while the peptonizing bacteria, 

 when they multiply without any check, carry on the decomposition too 

 energetically and to an undesirable extent; but in the presence of 

 lactic bacteria, which in a measure restrict and regulate the develop- 

 ment and the activity of the peptonizing bacteria, the joint efforts of 

 all these microorganisms give the desired result. 



From this point of view the chief care in the production of cheese 

 should be that both the peptonizing and the lactic bacteria are in the 

 curd, and that the proper conditions for their life activity are provided. 

 But the peptonizing bacteria, especially Bacillus subtilis, are very 

 widely distributed and multiply with extreme ease; therefore from a 

 practical standpoint no provision need be made for their presence and 

 attention should be confined to the lactic bacteria. 



