preferable) by inoculating the same with some of the original milk.
Not all abnormal fermentations are able, though, to compete with the
lactic acid bacteria, and hence outbreaks of this sort soon die out
by the re-establishment of more normal conditions.

=Factory contamination.= As the time element is of importance in the
production of troubles due to bacteria, it follows that infection of
milk on the farm is fraught with more consequence than factory
contamination, as the organisms introduced would have a longer
period of development. Nevertheless, the conditions in the factory
are by no means to be ignored, as they not infrequently permit the
milk to become seeded with highly undesirable types. A much more
rigid control can be exercised in the factory, where steam is at
hand as an aid in the destruction of organisms. In the cleaning of
pumps and pipes, steam is absolutely necessary to keep such
apparatus in a sanitary condition.

The water supply of the factory is a matter of prime importance, as
water is used so extensively in all factory operations. When taken
from a shallow well, especially if surface drainage from the
factory is possible, the water may be contaminated to such an extent
as to introduce undesirable bacteria in such numbers that the normal
course of fermentation may be changed. The quality of the water,
aside from flavor, can best be determined by making a curd test (p.
99) which is done by adding some of the water to boiled milk, and
incubating the same. If "gassy" fermentations occur, it signifies an
abnormal condition. In deep wells, pumped as thoroughly as is
generally the case with factory wells, the germ content should be
very low, ranging from a few score to a few hundred bacteria per
cubic centimeter at most. The danger from ice is much less, for the
reason that good daily practice does not sanction using ice directly
in contact with milk or cream. Then, too, water is largely purified
in the process of freezing, although if secured from a polluted
source, reliance should not be placed in this method of
purification, for even freezing does not destroy all vegetating
bacteria.

The ordinary house fly is an important source of contamination in
creameries, cheese factories and city milk plants. They are of
importance not only in increasing the number of fermentative
bacteria in milk but they may serve to contaminate it with
disease-producing organisms. The windows of all places where milk