1892.] Some Uses of Bacteria. 905 
in your cider. You let your cider stand in a barrel for sev- 
eral months, and little by little a change takes place in it; 
little by little the oxygen is taken out of the air and handed 
over to the alcohol, and when the alcohol gets hold of the 
oxygen it is no longer alcohol; it becomes acetic acid, and 
your cider is changed into vinegar. Now, it has been deter- 
mined that it is through the agency of bacteria that the alco- 
hol succeeds in getting hold of the oxygen. Bacteria grow 
on the surface of hard cider, forming a sort of scum, produ- 
cing, indeed, what we call “ mother of vinegar.” These bac- 
teria growing on the surface in some way take oxygen out of 
the air, pass it down into the fluid, give it to the alcohol, and 
when the alcohol gets hold of it it becomes acetic acid and 
you get vinegar where you originally had cider. The manu- 
facture of vinegar, then, is a process dependent upon the growth 
of bacteria. 
The manufacture of lactic acid is a process somewhat of the 
same character. Lactic acid is not a commercial article of 
very great importance, but still there are some factories in this 
country that manufacture it and put it upon the market to be 
sold for certain purposes. In the making of lactic acid the 
manufacturer makes constant use of bacteria. By the cultiva- 
tion of bacteria in milk the milk sugar is changed into lactic 
acid, which the manufacturer separates from the milk and 
puts upon the market. So you see that the manufacturer of 
lactic acid is wholly dependent upon bacteria; he could never 
produce it without their aid. 
Perhaps under this head of “ Miscellaneous ” I may just refer 
to a matter which is of considerable practical importance, and 
that is the matter of ensilage. We do not know very much 
about the theory in regard to the management of a silo at the 
present time, but we do know that the whole process of pro- 
curing proper and sweet ensilage is a process of properly man- 
aging bacteria growth. If you manage the bacteria growth 
correctly your ensilage will remain sweet and will become a 
food which is very desirable for your cattle; but if you do not 
manage the bacteria growth correctly your ensilage will decay, 
it will become sour, undergo fermentations, and you will suffer 
