s in butter are due to the action of acid cream
on iron or copper surfaces from which the tin has been worn. It is
equally important that attention be paid to the care of strainers,
coolers, and the small utensils. Cloth strainers are more or less of
a hotbed for bacterial growth, for unless they are boiled, and then
dried quickly and thoroughly, germ growth will continue apace in
them, as long as they contain any moisture.

=Milking machines and farm separators.= The introduction of these
special types of dairy machinery in the handling of milk on the farm
has materially complicated the question of the care of milk. Both of
these types of apparatus are much more complicated than the usual
milk utensil; consequently, the danger of imperfect cleaning is
thereby increased. This is still further accentuated by the fact
that cleansing of utensils on the farm can never be done so well as
at the factory or milk depot where steam is available. The milking
machine may be easily kept in a comparatively germ-free condition,
but unless this is done, it contributes its quota of germ life to
the milk.

The farm separator is more widely used than the milking machine and
in actual practice the grossest carelessness prevails in the matter
of its care. Frequently it is not taken apart and thoroughly
cleansed, but is rinsed out by passing water through the machine. It
is impossible by such a treatment to remove the slime that collects
on the wall of the bowl; the machine remains moist and bacterial
growth can go on. Such a machine represents a most important source
of contamination of milk and cream and it is probable that the
widespread introduction of the hand separator has contributed more
to lower the quality of cream delivered at the factory than any
other single factor.

=Contamination from factory by-products.= The custom of returning
factory by-products in the same set of cans that is used to bring
fresh milk is a prominent cause of bad milk. Whey and skim milk are
rich in bacterial life, and not infrequently are so handled as to
become a foul, fermenting mass. If the cans used to transport this
material are not scrupulously cleaned on the farm, transfer of
harmful bacteria to the milk is made possible. In this way the
carelessness of a single patron may be the means of seeding the
whole factory supply. This custom is not only liable to produce a
poor quality of milk, but it is more or less of a menace to all the
patrons of