es is similar to what happens in muddy water
upon standing. As the suspended particles fall to the bottom they carry
with them a large number of the organisms that are in the liquid.

~Various creaming methods.~ The creaming method has an important bearing
on the kind as well as the number of the bacteria that are to be found
in the cream. The difference in species is largely determined by the
difference in ripening temperature, while the varying number is governed
more by the age of the milk.

_1. Primitive gravity methods._ In the old shallow-pan process, the
temperature of the milk is relatively high, as the milk is allowed to
cool naturally. This comparatively high temperature favors especially
the development of those forms whose optimum growing-point is near the
air temperature. By this method the cream layer is exposed to the air
for a longer time than with any other, and consequently the
contamination from this source is greater. Usually cream obtained by the
shallow-pan process will contain a larger number of species and also
have a higher acid content.

_2. Modern gravity methods._ In the Cooley process, or any of the modern
gravity methods where cold water or ice is used to lower the
temperature, the conditions do not favor the growth of a large variety
of species. The number of bacteria in the cream will depend largely upon
the manner in which the milk is handled previous to setting. If care is
used in milking, and the milk is kept so as to exclude outside
contamination, the cream will be freer from bacteria than if
carelessness prevails in handling the milk. Only those forms will
develop in abundance that are able to grow at the low temperature at
which the milk is set. Cream raised by this method is less frequently
infected with undesirable forms than that which is creamed at a higher
temperature.

_3. Centrifugal method._ Separator cream should contain less germ-life
than that which is secured in the old way. It should contain only those
forms that have found their way into the milk during and subsequent to
the milking, for the cream is ordinarily separated so soon that there is
but little opportunity of infection, if care is taken in the handling.
As a consequence, the number of species found therein is smaller.

Where milk is separated, it is always prudent to cool the cream so as to
check growth, as the milk is generally heated before separating in order
to skim efficiently.

Although cream is n