364 MILK 



Lohnis in his classification of lactic acid bacteria groups 

 Streptococcus lacticus with Str. pyogenes Rosenbach. Kruse, as 

 stated before, was the first author to call attention to the similar- 

 ity of Bacterium lactis acidi Leichmann to pyogenic streptococci 

 and, therefore, proposed the name Streptococcus lacticus as more 

 suitable than Leichmann's appellation. Rolling states that a 

 sharp differentiation between Streptococcus lacticus, on the one 

 hand, and Str. pneumoniae and related streptococci, on the other 

 hand, cannot be made. He found among the strains of Str. 

 lacticus which he studied, some which grew as poorly on arti- 

 ficial media as Str. pneumonia, and some that produced such 

 small amounts of acid that milk coagulated slowly or not at 

 all. He was able to show that mice are sometimes killed by in- 

 jection of strains of Str. lacticus, and thinks that a close rela- 

 tionship between the two groups has been demonstrated. The 

 author expresses the belief that later work will show that Str. 

 pyogenes and Str. lacticus belong to the same "species," and that 

 perhaps suitable environmental conditions might render Str. lac- 

 ticus virulent for animals. The writer has shown that by repeated 

 passage through rabbits a high degree of virulence can be acquired 

 by Str. lacticus, although the opinion, erroneously quoted by some 

 authors, that Str. lacticus and Str. pyogenes are identical was 

 never uttered. A later investigation has shown that strains of 

 Str. lacticus can be rendered virulent so as to produce lesions in 

 rabbits practically identical with those produced by typical Str. 

 pyogenes, and that the fermentation reactions of Str. lacticus can 

 be altered by suitable conditions so as cause a clear approach to 

 other strains, including pathogenic strains as far as ability to 

 produce acid from carbohydrates is concerned. It was possible to 

 show that by animal passage and by cultivation in media contain- 

 ing serum without the presence of a carbohydrate the chain forma- 

 tion of Str. lacticus was favored so as to resemble the so-called 

 pathogenic Str. longus. Even the power to hemolyze human and 

 goat's blood was acquired to a limited extent at least. The power 

 to ferment carbohydrates with acid production was variable and 

 dependent in a measure on the oxygen pressure. The greater 

 the amount of oxygen available, the more readily were "carbo- 

 hydrates fermented. 



The morphology of streptococci is very variable, and a dis- 

 tinct classification on this basis cannot stand scrutiny. The cells 

 are known to appear in three distinct forms, namely: 1, the spheric; 

 2, the elongated, and 3, the flattened form. All these forms can 

 be observed in the same strain under varying conditions. The 

 length of the chain is perhaps even more variable than the shape 

 of the individual cell, and, therefore, cannot serve as an important 



