THE LACTIC-ACID BACTERIA 473 



and occasionally coagulation does not occur at all, but the milk 

 becomes thready or slimy. The lactic acid formed is generally of 

 the sinistrogyr variety. These bacteria grow in milk between 15 and 

 45 C., and best between 30 and 40 C. They often impart a dis- 

 agreeable taste to milk and occasionally milk containing them in 

 very large numbers causes vomiting. These bacteria ferment other 

 sugars, in addition to lactose, and then form, besides lactic acid, also 

 succinic, acetic, and some formic acid; they also sometimes form 

 alcohol and carbon dioxide and hydrogen. The several types in this 

 first group are represented as follows: 



Type 1. Gas formers: Bacillus acidi lactici Hiippe, Bacillus 

 lactis aerogenes Escherich, Grotenfeld's Bacillus acidi lactici, the 

 fan-bacillus of Clauss, and Lustig's typhoid-like bacillus. 



Type 2. These coagulate milk but do not form gas: Bacterium 

 Hmbatum of Marpmann, Bacillus sputigqnes of Pansini and several 

 others. 



Type 3. No coagulation, but formation of gas. The principal 

 representative of this type is the Bacillus pneumonise of Friedlander. 



Type 4- This is represented by Bacillus lactis inocuus of Wilde, 

 Bacillus No. 14 of Conn, Bacterium cocciform of Migula, and others. 

 Neither coagulation nor gas is produced. 



BACILLUS LACTIS Viscosus. There are several other types of 

 organisms in the first group of lactic-acid producers which make milk 

 slimy or which liquefy the casein subsequent to its coagulation. Many 

 bacteria of the first group are so intimately related to the colon bacillus 

 that a separation from it becomes impossible. The most important 

 organism of the kind which make milk slimy or ropy is the Bacillus 

 lactis viscosus of Adametz. The organism has been isolated from 

 water which probably is its normal habitat and from which it gets 

 into milk. Ward has always found this organism in slimy milk. It 

 grows at very low temperatures, better than at higher temperatures, 

 and for this reason its multiplication is favored by the rapid cooling 

 of milk. It possesses a gelatinous, slimy capsule and forms zoogleal 

 masses; it is this property which imparts to milk the slimy, ropy 

 character. Such milk is probably not unwholesome, but it is repulsive 

 and disliked by consumers. 



Bacteria of Group II. The second group, known as the strepto- 

 coccus group, comprises cocci which are not motile, form no spores, 

 are either round, semiglobular or oval and form shorter or longer 

 chains. They are Gram positive and frequently show a capsule. 

 There are pathogenic and non-pathogenic bacteria in this group, the 

 former growing best at 37 C., the latter at 30 to 35 C. They 

 develop both aerobically and anaerobically. They generally form 

 much lactic acid and coagulate milk; sometimes both processes occur 

 slowly. Coagulation is sometimes brought about by an enzyme of 

 the rennet type without the formation of acid. The lactic acid 

 formed is generally of the dextrogyr variety. These bacteria also 



