refore
visible dirt is, however, regarded of sufficient value to warrant
the use.

Machines designed especially for the clarification of milk are now
widely used. They differ from the cream separator in that the milk
is introduced at the outside of the bowl and hence there is no
separation of the fat from the serum. It is claimed that the removal
of the dirt, cells from the interior of the udder and bacteria is as
efficiently done as when the separator is used. The advantages
claimed for the machine are that it has no effect on the subsequent
gravity creaming of the milk and that less power is demanded than
for the separator.

From the standpoint of the consumer, all processes by which dirt is
removed from milk are objectionable, since they make the milk
appear cleaner and better than it really is, the harm having been
done when the dirt with the adherent bacteria found its way into the
milk. The removal of the foreign matter that has been introduced
into the milk will have but little effect in reducing the number of
bacteria, since a large part of the organisms will have been washed
off the insoluble material. All of these processes improve the
appearance of the milk but have little or no influence in increasing
its keeping quality or its healthfulness.

=Preservation by cold.= The only legitimate way of preventing the
growth of bacteria in milk is by holding it at temperatures at which
the ordinary forms of bacteria cannot thrive. Bacterial growth is
greatly checked at temperatures approximating 50 deg. F., or below,
although certain types multiply at the freezing point or slightly
above. If food products are actually congealed, no germ growth
occurs, and they may be kept quite indefinitely, but this process
cannot be successfully applied to milk, as the fat and casein are
physically changed, so that a normal emulsion can not again be made
when the frozen milk is melted. The fat separates in visible masses
as though the milk had been partially churned. On account of this
fact milk must be stored at temperatures above the freezing point.
In Denmark efforts have been made to preserve milk, that is to be
shipped long distances, by freezing a portion of the milk, and
placing a block of the frozen milk in each can after cooling the
main mass of milk nearly to the freezing point. Even this method has
not proven practical, and at present reliance is placed on thorough
chilling of the milk. At 32 deg. F., the lactic bact