1 56 FERMENT A TION IN MILK 



bacillus which he named the Bacillus acidi lactici. This, was 

 probably identical with Lister's bacillus, and is now a term 

 used to cover a whole family of organisms having somewhat 

 similar characters and possessing the property of setting up lactic 

 fermentation.^ 



In 1894 Giinther and Thierfelder published the result of their 

 work on lactic acid fermentation, from which they concluded that 

 Lister and Hueppe had discovered one and the same species, and 

 that it was the causal agent of lactic acid production in Europe. 

 Esten found a similar organism to be the cause of lactic acid 

 fermentation in America, and Conn holds that three organisms, 

 or rather types of species, are the chief agents in the production 

 of lactic fermentation, namely B. acidi lactici, Nos, i. and ii., and 

 B. lactis cBrogenes. The first named forms between 75 to 90 per 

 cent, of the bacteria present. No. ii. is also very abundant. 

 B. lactis cerogenes is found almost universally, although never in 

 large numbers. It is a type of a species which produces intense 

 acid on litmus gelatine cultures, produces much gas in milk or 

 milk sugar broth, curdles milk at high temperatures, and produces 

 a distinctive odour in the milk, which it ferments.'^ According to 

 Escherich, the formation of lactic acid by this organism prevents 

 fermentation in the stomach and intestines. 



It was Hueppe who made the important discovery that many 

 different species of bacteria are capable of setting up lactic fer- 

 mentation, and what we have now said amply supports that view. 

 Indeed, it has been estimated that upwards of 100 different 

 bacteria possess this property.^ A description of the more impor- 



^ Hueppe isolated five forms of his lactic acid bacillus. Maddox, Beyer. 

 Fokker, Krueger, Grotenfeld, and other workers isolated lactic acid organisms. 



^ Storr's Agricultural Expt. Sta. Rep., 1899, p. 22. Others than those 

 named are B. acidi lactici of Giinther, B. acidi lactici of Leichmann, Bacillus 

 xix. of Adametz, Bacillus a. of Freudenreich, B. and M. acidi Icevolactici of 

 Leichmann, Grotenfeld's B. acidi lactici Nos. i. and ii., No. 8 of Eckles, and 

 Bad. casei. 



^ Delbriick, Zopf, Krause, Peters, Lindner, Weigmann, Storch, and Marp 

 mann, are amongst those who, in addition to workers we have named, have 

 described bacteria possessing the power of setting up lactic fermentation, j 

 Only provisional classifications are possible at present, as, owing to variations 

 in biology and terminology, it is probable that certain lactic organisms are 

 described under several different terms. Generally, it may be said that some 

 grow well in the presence of oxygen, and others do not. The latter group, 

 fa culta tivg anaerobes, are perhaps the most common. They sour milk best in 

 deep vessels, and produce a right-handed lactic acid. I They are widely distri- 

 buted in nature, and may form 90 per cent, of the total bacteria in milk. Some 



