utter. The butyric acid bacteria are
anaerobic, and thus can grow in butter and cheese away from the air.

=Slimy or ropy fermentation of milk.= A slimy or ropy condition of
milk is frequently noted on the farm and in the dairy. Several
causes for this abnormal condition exist. Sometimes the milk may be
slimy when milked from the cow. This occurs most frequently in the
case of inflammation of the udder which may or may not be due to
bacteria. The direct cause of the abnormal condition in milk is the
presence of fibrin and white corpuscles from the blood which form
masses of slimy material; in such cases the trouble does not
increase in intensity with age, nor can it be propogated by
transference to another sample of fresh milk.

[Illustration: Fig. 22.--Slimy Milk.

It does not mix with water when poured into it.]

Another type of slimy milk is produced by the growth of certain
types of bacteria which enter the milk after it is drawn from the
udder. These may come from various sources. The bacteria concerned
belong to two groups: (1) those that grow best in the air and do not
form acid; (2) those that grow in the absence of air, throughout the
entire mass of milk and which form acid. The slimy condition is
noted in the milk only after the milk has been stored for some time;
it usually increases with the age of the milk and can be produced
in a second sample by transferring a little of the slimy milk to it.

The fermentation produced by the aerobic bacteria is most often met
in bottled milk and cream during the warmer times of the year. On
account of their relation to oxygen, the growth is confined to the
surface of the milk and only the upper layer becomes slimy; thus
when the cream is removed, the abnormal condition is noted. The
sliminess is due to the mass of bacterial growth rather than to the
production of any specific substance in the milk. This trouble may
be of considerable economic importance to the dealer, as such
abnormal milk is objectionable for ordinary use, but as far as is
known, it is incapable of affecting the health of the consumer.

In numerous outbreaks of this trouble the source of contamination
has been traced to infection from well water or a stream, as the
organisms causing the trouble are found naturally in water. Keeping
the milk in a tank in the pump house sometimes permits of troubles
of this sort, the water used for cooling giving opportunity for
contamination. Cattle wading in a str