230 AGRICULTURAL BACTERIOLOGY. 



effect upon butter flavor. A few may be looked upon as 

 favorable and a few as unfavorable. 



Since the bacteria in cream are so varied in their action, it 

 may, perhaps, be a matter of little surprise that the ordinary 

 process of cream-ripening is so likely to give a good result, 

 and that without any artificial means of controlling the species 

 of bacteria, a butter-maker can so commonly obtain a good 

 product. The reason for this is apparently three-fold. In the 

 first place, although the number of species which produce a 

 favorable cream-ripening is apparently not so very great, 

 they are species which are most common around an ordinary 

 well-kept dairy. Consequently, if care is taken to keep the 

 dairy in good condition, it is most likely that cream will be 

 especially supplied with the species of bacteria which produce 

 good results, and it is only under unusually improper condi- 

 tions that the unfavorable species become abundant. Secondly, 

 there are reasons for believing that the species of bacteria 

 which produce good results, under ordinary circumstances 

 prove to be more vigorous than the others and grow so rap- 

 idly as either to crowd the others out of existence or to coun- 

 teract any effect which they may produce. We have already 

 noticed how the lactic bacteria, because of their greater vigor, 

 grow so rapidly in the milk as to overcome the other bacteria. 

 This occurs also in cream and to such an extent that cream, 

 which at first has only a few lactic bacteria, may, at the end of 

 ripening, contain over 99 per cent, of these organisms. This 

 is a very significant fact in cream-ripening. Thirdly, the tem- 

 perature used in ripening cream is such as to stimulate the 

 growth of the favorable species, while it checks the growth of 

 many other bacteria. Thus, the process of cream-ripening is 

 commonly satisfactory. But although this is the case, butter- 

 makers, the world over, are ever and anon troubled with an 

 improper type of cream-ripening, and this makes it very de- 

 sirable that, if possible, some means of controlling this process 

 should be placed in their hands. 



