BACTERIA IN BUTTER-MAKING. 187 
mined by experiment. This method is, of course, logically 
satisfactory, for, since pasteurization destroys most of the bacteria 
present in the cream, it follows that the ripening will be produced 
by the species of bacteria introduced by the adding of the pure 
culture. Professor Storch was soon followed by other experimenters 
and the method adopted in Copenhagen was extended more or less 
widely in north Germany and Denmark. In Denmark it is now 
used almost universally, and in north Germany quite widely, in 
general dairying. 
In the United States the use of pure cultures for cream-ripening 
has had a somewhat different history. It was introduced to dairy- 
men shortly after its development in Copenhagen, but for some 
time little attention was paid to it, so that it was hardly brought to 
the notice of the ordinary butter-maker. Our butter-makers were 
not in condition to pasteurize their cream. In 1895 a slight change 
was made in the process. In order to bring the subject more 
widely to the attention of dairymen, a method was suggested of 
using the cultures without previously pasteurizing the cream. 
This seemed illogical, since the cream is already filled with bacteria, 
and the addition of a new culture could hardly be supposed to give 
entirely satisfactory results. But when we remember how a vigorous 
lot of lactic acid bacteria can overcome other species, the method 
does not appear so illogical after all. With this change our butter- 
makers were willing to try pure cultures and in a short time American 
butter-makers learned of their meaning and began to experiment 
with them widely. The result of the dozen or so years of experience 
has been to show the extreme value of starters as a means of controll- 
ing the ripening, until to-day starters of some kind are almost univer- 
sally used in -all good creameries and dairies. 
Preparation of Starters. While starters are very widely 
used to-day, they are not always pure cultures. Two quite different 
methods of preparing them are in use. 
Natural Starters. A natural starter is nothing more than some 
normally soured milk. In order to obtain it it is only necessary 
to select several quarts of good milk and place it in a clean, sterilized 
pail or can, covered to keep out the dust, and keep it in a temperature 
