y 

 * * 



418 Bacteria in Relation to Country Life 



cause of the changes observed. It was thought that the 

 organisms themselves or the enzymes produced by them, 

 accomplished the digestion of the curd. There was a 

 strong difference of opinion, however, as to the kinds 

 of bacteria responsible for the important transforma- 

 tions. Some bacteriologists asserted that the digestion 

 was performed by peptonizing bacteria, while others 

 maintained that it was effected by the lactic -acid bac- 



teria. In order to decide 

 the point at issue, various 

 organisms occurring in 

 % * cheese were isolated in pure 

 culture and were employed 



I for the ripening of sterile 



V4 I V^ X ^^ curd. Large numbers of 



^v I o^v^ such experimental cheeses 



^Si ' were prepared and studied, 



Fig . 63. Lactic acid ferments in -, . , r > , , 



cheese -ripening. 1. Bacterium and it Was lOUnd that in 

 lactis acidi; X 3,000. 2. Bacillus , . , , r -i i 



A; x 3,000. 3. Bacillus casei T- most instances they tailed 



X 3,000. 4. Bacillus casei A; . 11 m i 



x 3,000. (Freudenreich and to ripen normally. To be 



Thoni.) T^, -, . , . ^ ., 



sure, rreudenreich, in Switz- 



erland, was able to secure a partial ripening of cheese 

 made out of pasteurized milk and inoculated with pure 

 cultures of lactic-acid bacteria, yet the results were not 

 fully satisfactory. Moreover, cheese made from boiled 

 milk and similarly inoculated failed to show any ap- 

 preciable ripening. Other investigators were believed 

 to have secured more or less satisfactory ripening, with 

 the aid of peptonizing bacteria, but their results were, 

 in no case, above criticism. 



Meanwhile, the investigations of Babcock and Rus- 



