66 STORRS AGRICULTURAL EXPERIMENT STATION. 
INVESTIGATIONS ON THE SOURCES OF THE ACID 
ORGANISMS CONCERNED IN THE 
SOURING OF MILK. 
BY ROLLIN H. BURR. 
Investigations of the acid organisms of milk date back to 
1877, when Lister discovered in milk an organism which he 
called Bacterium lactis. Subsequently Hueppe isolated and 
made a more careful study of what was probably the same 
organism, and named it Baczllus acidt lactice. After him Marp- 
mann, Grotenfelt, Keyser, and many others, isolated from 
souring milk bacteria agreeing with this bacillus, while other 
investigators have found in sour milk many different organisms 
capable of producing lactic acid, but not resembling the organ- 
ism of Hueppe. It was, therefore, for a time believed that 
there is no distinct lactic bacterium concerned in the souring 
of milk, but that there is quite a large number of such bacteria 
any one of which may be concerned in the milk souring. The 
~ work of more recent years has, however, shown that this is 
hardly correct. In 1894 Gunther and Thierfelder published 
the result of work,. from which they concluded that the organ- 
ism of Lister and Hueppe was the common cause of the normal 
souring of milk in Europe. Since then other confirmatory 
experiments have been published. Esten, in 1896, published 
the results of investigations made upon milk from various 
parts of the United States, from which he concluded that the 
ordinary souring of milk in this country is due chiefly to one 
organism.* This bacterium is probably identical with that 
found by Gunther and Thierfelder, and was given the same 
name by Esten, &. acidi lactict, It has been more recently 
found that associated with this species in this vicinity are two 
other lactic bacteria found almost universally and contributing 
to the souring of milk, although commonly present in far less 
numbers. ‘These two are B&B. lactis aerogenes and a species 
* Storrs Station Report, 1896, p. 44. 

