red that these grosser _visible_ particles of pollution are
not really the cause of the troubles which may ensue in improperly
handled milk. The bacteria which are adherent to these foreign
particles are in large measure washed off in the process of
straining, and pass through the meshes of the finest strainer. The
main service, therefore, of straining is to improve the appearance
of the milk, and it has no effect on the quality in any way.

=Production of clean milk.= The problem of clean milk is important,
whatever may be the use to which milk may be put. It is important in
the manufacture of butter, but owing to the fact that the fat is not
readily acted upon by bacteria, it is not so sensitive to bacterial
conditions, as when the milk is made into cheese. In this product,
the bacterial condition of the milk is a matter of prime importance.
In milk destined for direct consumption, the exclusion of the
bacteria becomes yet more important. While it is impossible to
exclude bacteria so completely that milk will not undergo
fermentative changes, yet for domestic consumption it is preferable
to have milk with as low bacterial content as can readily be
secured. The highest type of market milk, that known as sanitary, or
certified, is produced under such extreme conditions of care as to
contain the minimum germ content. To accomplish these results
requires such stringent control as to increase greatly the cost of
the product. Pure, clean milk can be produced at a very slight
increase in cost over the regular expense of milk production, if the
right kind of attention is given to certain details of a practical
character. Improvement in our milk supplies must largely come from
this source, for any improvement to be permanent must be made to
pay, and it requires considerable education to secure the
co-operation of consumers and their willingness to pay for any
material increase in the quality of the product.

In the foregoing factors concerned in the contamination of milk, it
is of course impossible to measure accurately the influence of the
different sources of infection, as these are continually subject to
variation in every case. As a rule, the most important factors are
those pertaining to the utensils and the condition of the animal
herself. If these two factors are brought under reasonable control,
the major portion of contamination that ordinarily obtains is done
away with. The application of the remedial or preventive