a factory, inasmuch as the opportunity always obtains
that disease-producing organisms may thus be introduced into the
supply. Not infrequently is tuberculosis thus spread through the
medium of factory by-products.

[Illustration: Fig. 8.--Whey Disposal.

Whey barrels at a Wisconsin Swiss cheese factory. Each patron's
share is placed in a barrel which is so situated that it is
impossible to empty it completely; thus it is not cleaned during the
season.]

The manufacture of Swiss cheese presents a striking example of the
disregard which factory operators show toward the employment of
bacteriological principles. In these factories, the custom is widely
practiced of apportioning the patrons' allotment of whey into
individual barrels which are supposed to be emptied each day. As
these barrels are, however, rarely ever cleaned from the beginning
to the end of the season, they become very foul, and the whey placed
in them from day to day highly polluted. It is this material which
is taken back to the farms in the same set of cans that is used for
the fresh milk. When one recalls that the very best type of milk is
essential for the making of a prime quality of Swiss cheese, and
that to secure such, the maker insists that the patron bring the
product to the factory twice daily, the before mentioned practice
appears somewhat inconsistent.

=Treatment of factory by-products.= To overcome the danger of
infecting milk from factory by-products with either undesirable
fermentative organisms, or disease-producing bacteria, the most
feasible process is to destroy these organisms by the application of
heat. In Denmark, some portions of Germany, and in some of the
states in this country, laws exist which require the heating of all
skim milk before it is returned to the farm. This is done by the
direct use of exhaust steam, or running the product through heaters.

The treatment of whey in cheese factory practice is especially
important since the warm whey must be stored for a number of hours
before it is returned to the farms. Even under the best of
conditions the whey is certain to be in an advanced state of
fermentation when placed in the milk cans, and it only needs the
infection of the whey tank with harmful bacteria to cause great loss
on account of the injury of the product by these bacteria. Among
Canadian factories the custom of heating the whey as it passes from
the cheese vat to whey tank has been introduced, and where ev