uently as circumstances will permit.

[Illustration: Fig. 9.--Bacteria on Hairs.

Each colony on the hair represents one or more bacteria that were
adherent to the hair when it was placed on the surface of the solid
culture-medium.]

The animal contributes materially to the quota of germ life finding
its way into the milk through the dislodgment of dust and filth
particles adhering to its hairy coat. The nature of this coat is
such as to favor the retention of these particles. Unless care is
taken, the flanks and udder become polluted with fecal matter, which
upon drying is displaced with every movement of the animal. Every
hair or dirt particle so dislodged and finding its way into the
milk-pail adds its quota of organisms to the liquid. This can be
readily demonstrated by placing cow's hairs on the moist surface
of gelatin culture plates. Almost invariably bacteria will be found
in considerable numbers adhering to such hairs, as is indicated in
Fig. 9.

Dirt particles are even richer in germ life. Not only is there the
dislodgment of hairs, epithelial scales, and masses of dirt and
filth, but during the milking process, as at all other times, every
motion of the animal is accompanied by a shower of _invisible_
particles, more or less teeming with bacterial life. All of this
material contains organisms that are more or less undesirable in
milk. Bacteria concerned in gassy fermentations and those capable of
producing obnoxious taints are particularly common, so that this
type of pollution is especially undesirable in milk.

=Amount of dirt in milk.= When one remembers that the larger part of
fresh manure is of such a nature that it does not appear as
sediment, the presence of evident filth in milk must bespeak
careless methods of handling.

The sediment or dirt test is used quite extensively to ascertain the
amount of dirt milk may contain. By means of a cotton filter, the
insoluble residue is removed and is made evident upon a layer of
absorbent cotton. Milk that would show with difficulty any evidence
of dirt upon ordinary examination reveals such defects very readily
in this test.

=Exclusion of dirt.= It is better to keep bacteria out of milk, so far
as practicable, rather than to attempt to remove them after they
have once gained entrance. As is usual, prevention of trouble is
much more easily accomplished than removing the difficulty after it
once occurs.

[Illustration: Fig. 10.--Dirt from Milk.

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