112 Transactions of the Canadian Institute. [Vol. VII. 



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 Oidiutn lactis, 

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

 in the ripening of cheese ; they yield soluble proteids and decompose 

 albuminous compounds with the formation of ammonia and volatile 

 acids corresponding to those occurring in the 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 

 analysis of Bondzinsky, viz.: that there is in cheese only a small quantity 

 of peptone which is not precipitated by ammonia 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 micro-organisms, the casein is con- 

 verted almost entirely into peptone. In view of these opposing facts, 

 the author concludes that the joint action of the peptonizing bacteria 

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

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

 future investigations of the process. 



The lactic acid bacteria are not capable of producing this process, 

 while the peptonizing bacteria, when they multiply without any check, 

 carry on the decomposition too energetically and to an undesired extent, 

 but in the presence of lactic bacteria, which in a measure restrict and 

 regulate the development and activity of the peptonizing bacteria, the 

 joint effort of all these micro-organisms gives the desired results. 



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 the 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 acid bacteria. 



Having defined the part which the peptonizing bacteria play in the 

 ripening of cheese, the question still remains unsettled whether these 

 bacteria, which are according to de Freudenreich present in hard cheese 

 in small numbers, act as such in the process of ripening, or by means of 



