le
lot soon becomes tainted. If this waste product is returned to the
different patrons in the same cans that are used for the fresh milk, the
probabilities are strongly in favor of some of the cans being
contaminated and thus infecting the milk supply of the patrons. If the
organism is endowed with spores so that it can withstand unfavorable
conditions, this taint may be spread from patron to patron simply
through the infection of the vessels that are used in the transportation
of the by-products. Connell has reported just such a case in a Canadian
cheese factory where an outbreak of slimy milk was traced to infected
whey vats. Typhoid fever among people, foot and mouth disease and
tuberculosis among stock are not infrequently spread in this way. In
Denmark, portions of Germany and some states in America, compulsory
heating of factory by-products is practiced to eliminate this danger.[3]

~Pollution of cans from whey tanks.~ The danger is greater in cheese
factories than in creameries, for whey usually represents a more
advanced stage of fermentation than skim-milk. The higher temperature at
which it is drawn facilitates more rapid bacterial growth, and the
conditions under which it is stored in many factories contribute to the
ease with which fermentative changes can go on in it. Often this
by-product is stored in wooden cisterns or tanks, situated below ground,
where it becomes impossible to clean them out thoroughly. A custom that
is almost universally followed in the Swiss cheese factories, here in
this country, as in Switzerland, is fully as reprehensible as any dairy
custom could well be. In Fig. 7 the arrangement in vogue for the
disposal of the whey is shown. The hot whey is run out through the
trough from the factory into the large trough that is placed over the
row of barrels, as seen in the foreground. Each patron thus has allotted
to him in his individual barrel his portion of the whey, which he is
supposed to remove day by day. No attempt is made to clean out these
receptacles, and the inevitable result is that they become filled with a
foul, malodorous liquid, especially in summer. When such material is
taken home in the same set of cans that is used to bring the fresh milk
(twice a day as is the usual custom in Swiss factories), it is no wonder
that this industry is seriously handicapped by "gassy" fermentations
that injure materially the quality of the product. Not only is the above
danger a very consid