200 BACTERIA AND OTHER MICROORGANISMS IN CHEESE. 
ferments which they have produced may continue their activity until 
they finally produce the new products that give the flavor. 
One fact appears to be certain amid much that is still unsettled. 
The lactic acid organisms certainly play an important part in the 
process; at least in the ripening of the Cheddar cheeses and probably 
the other hard cheeses as well. The lactic acid developed in the 
early ripening cheese is necessary to the digestive changes that occur, 
for the acid combines with the casein, a preliminary step in the 
ripening. While their total action is not yet understood, it is 
certain that they have a necessary part in the cheese-ripening. 
As a result of these facts, cheese-makers have, in recent years, 
learned that the use of lactic acid starters is decidedly advantageous. 
This practice enables the cheese-maker to control much more 
accurately the ripening, and to reduce the number of failures. The 
reason why the inoculation of a lactic starter tends to reduce the 
failures in cheese-making can easily be understood from the facts 
already presented. The lactic acid bacteria have the power of 
checking the growth of other germs, and even of destroying them 
altogether. When, therefore, the milk has a large quantity of 
lactic bacteria developing rapidly in the curd, the other bacteria, 
which might under different circumstances produce putrefaction, 
are prevented from increasing. In the making of cheeses this 
protecting action of the lactic bacteria becomes very important, 
and is, indeed, the secret of good cheese. The cheese remains for 
weeks, or even months, in a moist condition, and there is opportunity 
all this time for the growth of bacteria. If a proper lactic organism 
is present at the outset, the cheese will be protected from the various 
putrefactive types that would otherwise surely injure it. Their 
presence in sufficient quantity is responsible for many of the defects 
to be noticed later. 
For these reasons, then, the cheese industry is learning the 
prime importance of a strong lactic fermentation in milk that is to 
be converted into cheese, and in order to bring this about it is 
rapidly adopting the method of using starters. Cheese starters are 
essentially identical with those used in butter-making, and they are 
used in much the same way. Home starters are frequently made 
