INVESTIGATIONS OF ACID ORGANISMS OF MILK. ‘67 
which Conn has called 2. acidi lactict I7.* 'These three organ- 
isms are apparently the only common organisms concerned in 
the souring of milk in this region. 
THE IMPORTANCE OF A KNOWLEDGE OF THE SOURCES OF 
THESE ORGANISMS. 
For a number of reasons it is particularly important to know 
the source of the acid organisms in milk. In the first place, 
the industry of furnishing sweet milk to cities finds in the 
lactic bacteria its greatest obstacle. In warm weather particu- 
larly, in spite of all that can be done, milk is almost sure to 
sour. If it could be definitely shown where these lactic organ- 
isms come from, it might be possible to devise simple means of 
guarding against them and thus aiding in the process of pre- 
serving milk. 
In the ripening of cream for butter making the problem of 
milk bacteria is of no less importance. It has been quite 
definitely shown that the flavors of the butter are due to the 
character of the ripening, and that the character of the ripen- 
ing depends, in considerable degree at least, upon the kind of 
bacteria which'chance to be present in the cream. ‘The varie- 
ties of bacteria present in normal cream during ripening are 
numerous, but, as is shown in an article by Conn and Hsten 
in this Report,t the lactic bacteria play a very important part 
in this proéess: 
In the use of artificial cultures for cream ripening, adopted 
quite widely in some countries, it has been found necessary to 
-pasteurize the cream in order to get rid of the noxious bacteria 
that chance to be present and then subsequently to inoculate 
with an artificial culture. In the article just referred to it has 
been shown that in ripened cream 2. aczdi lactict (Esten) com- 
prises commonly 90 per cent. or more of the organisms present, 
the numbers being small in the fresh milk and cream, but 
under normal conditions increasing rapidly until the milk or 
cream sours and curdles. Evidently if the source of these as 
well as the other lactic organisms could be accurately deter- 
mined it might be possible to keep them out of milk, and if 
this could be done the problem of the use of artificial cultures 
would be very greatly changed. 

* Storrs Station Report, 1899, pp. 13-67. + See pp. 13-33. 
