474 THE LACTIC ACID BACTERIA 



split up other sugars, but they generally form lactic acid only, rarely 

 other acids. This group again contains a number of types distin- 

 guished and represented as follows : 



Type 1. Streptococcus mastiditis coagulates milk and forms gas. 



Type 2. Streptococcus Guentheri or Leichmann and Strepto- 

 coccus lacticus Kruse both coagulate milk, but do not form gas. 

 These two organisms are probably the most common and most important 

 lactic acid bacteria of milk. 



Type 3. Streptococcus Kefir, does not coagulate milk and does 

 not form gas. 



Type 4- Streptococcus lactis inocuus, does not coagulate and does 

 not form gas. 



Type 5. Leuconstoc mesentericus and Micrococcus mucilaginosus 

 of Schiitz and Ratz, which make milk slimy. 



Type 6. Streptococcus mirabilis Roscoe, which is an arborescent 

 organism. 



Type 7. Streptococcus coli gracilis and coli brevis, which are 

 liquefiers. 



Bacteria of Group III. The bacteria of the third group vary much 

 in length. They are most commonly slender rods, 2 to 3 micra long 

 and 0.5 to 0.75 micron wide. Some of them form filaments or pseudo- 

 filaments 50 or more micra long. They are generally not motile, 

 never form spores, rarely show a capsule, and are Gram positive. 

 They are either preferably or even strictly anaerobic. Their optimum 

 temperature is generally quite high, between 40 and 50 C., their 

 minimum at 25 C. or somewhat lower. Milk is generally coagulated 

 very slowly; the lactic acid formed is generally sinistrogyr. None 

 of them are disease producers. They are divided into types, the 

 most important of which are : 



Type 1. Bacillus casei of Freudenberg. 



Type 2. Bacterium casei of Leichmann. 



Type 3. Bacterium caucasicum. 



Type 4. Bacillus Delbrucki. 



Type 5. Bacillus Aderholdi. 



Type 6. Bacillus lactis acidi Leichmann. 

 There are no liquefying bacteria represented in this group. 



Bacteria of Group IV. The bacteria of the fourth group are of the 

 type of the Micrococcus pyogenes Rosenbach or Micrococcus lactis 

 acidi. They are cocci varying in size from 0.8 to 1.6 micron. They 

 are single, in pairs, or in irregular groups (staphylococci). They do 

 not form spores, are Gram positive, have their optimum of growth 

 between 20 to 30 C., and multiply best in the presence of oxygen. 

 Some of them liquefy gelatin, others do not. Most of them coagulate 

 milk. Formation of gas is rare. The types in this group are repre- 

 sented by the following bacteria: 



Type 1. Micrococcus acidi Leischmann. 



Type 2. Micrococcus lactis acidi Marpmann. 



