IDENTITY OF THE LACTIC-ACID STREPTOCOCCUS 



159 



Although it might appear that chain formation is of some 

 value in distinguishing the lactic-acid bacteria from other 

 streptococci, we do not wish to make that claim. Such a differ- 

 entiation would at best be a doubtful one. The method used 

 in collecting cultures for this work was such as would tend to 

 introduce an error in this phase of the study; only cultures 

 which showed typical chain arrangement were selected as repre- 

 senting the udder-type of streptococcus, while no attention was 

 paid to morphology in selecting the lactic-acid type. As was 

 noted before, chain formation is not a very constant character. 

 In this study there was apparently no correllation between the 

 lactic cultures which grew in chains on broth and those which 



did so on agar, and it is doubtful if they would show much 

 constancy in this respect on the same medium. 



ACTION ON MILK 



The amount of acid produced in milk, the presence of coagu- 

 lation and the time required for curdling were noted. All of 

 the cultures produced sufficient acid to cause the coagulation 

 of milk when tested at 37°C. As may be seen from table 2, 

 the organisms of the first group (cultures 1 to 50) showed a 

 more prompt clotting of milk than did those of the second 

 group. At 37°C. all but 3 in the first group curdled milk within 

 twenty-four hours, while only 10 of the other group acted so 

 promptly. 



The maximum acidity produced in milk was tested by incu- 

 bating the cultures for ten days at 35°C. The acidity developed 



