each
can.

All creameries handling milk of different grades will be required to
demonstrate to the Department of Health that they are capable of
keeping the grades separate, and must keep records satisfactory to
the Department of Health concerning the amount of milk of each grade
handled each day.

It is to be noted that the grades of milk are based on the bacterial
content of the milk and on the opportunity for the milk to become
contaminated with pathogenic organisms. From the statements made in
a previous chapter it is evident that the number of bacteria in any
sample of milk is dependent upon (1) the original amount of
contamination, (2) the age of the milk, and (3) the temperature at
which it has been held. A high bacterial content is indicative of
poor milk, while a low bacterial content can be obtained, in the
case of raw milk, only where due attention is paid to cleanliness
and cooling. This relation between the quality of milk and its
bacterial content has led many cities to adopt numerical bacterial
standards, even when grades of milk have not been established.
Boston requires that the milk shall not contain more than 500,000
bacteria per cubic centimeter. Rochester, N. Y., has a standard of
100,000 per cubic centimeter, while Chicago requires that the milk
on arrival in the city shall not contain more than 1,000,000 per
cubic centimeter from May first to September thirtieth, and not over
500,000 between October first and April thirtieth. The sale of milk
containing more than 3,000,000 bacteria per cubic centimeter is
prohibited.

It has been urged that bacterial standards are not of value since
the healthfulness of milk depends on the kind of bacteria present
rather than on the number. It is well recognized that milk
containing millions of acid-forming organisms, butter milk, is a
healthful food, while that containing many less bacteria may contain
some disease-producing organisms. It has been urged that a
qualitative standard should supplant the quantitative. The consumer
desires milk that has been produced under clean conditions, and
which has good keeping qualities. The harmless forms of bacteria
exert the greatest influence on the keeping quality. Experience has
shown that the quantitative examination of the milk supply as
it comes from the farm is the most feasible method of determining,
in the laboratory, whether the farmer has obeyed the rules
with reference to cleanliness and cooling of the mil