ay be used with effect. The hands should be washed before milking
as milk is certain to come in contact with them to some extent. The
milking should be done with the whole hand rather than stripping
between the thumb and finger; the clothing should be covered with
clean overalls and jumper, or at least a clean apron should be worn
during the milking. If these are of white material, more frequent
laundering is likely to result.

=Contamination from air.= It is difficult to disassociate the
contamination arising from the condition of the air from that
derived directly from the animal. Barn operations of various kinds
result in the production of dust, particularly where dry forage,
such as hay or straw, is handled. Where manure is given an
opportunity to dry, dust is readily produced, and such material is
particularly replete with bacterial life. Some kinds of dust, such
as that originating from ground grains, or shavings that may be used
for bedding, contain a small amount of bacterial life in comparison
with the dust from hay, or other dry fodder. In a dried condition,
the slightest movement is apt to dislodge these fine particles, and
they float in the air for considerable periods of time. If milk is
drawn and exposed to the air of the barn during the feeding
operations, it is subject to the dust shower that is present. Where
the storage can is allowed to stand in the stable during the
milking, even though it is covered with a strainer, this
accumulation of microscopic particles is added to the milk, as they
readily pass the meshes of the finest strainer.

[Illustration: Fig. 15.--contamination From the Air.

This culture plate, three inches in diameter, was exposed for 30
seconds in the barn during feeding of dry fodder. A 12-inch pail
exposes over 18 times the surface of this plate.]

=Removal of dirt after introduction.= The more primitive method of
improving the quality of milk, so far as its dirt content is
concerned, is to attempt to remove the grosser particles of
contamination after entrance. In the case of straining, the method
is usually applied at the time of milking, but in the case of
filtering and clarifying, it is carried out at the milk station, in
an effort to improve the appearance of milk and overcome the
influence of careless methods of the producer. By the use of
strainers, either metallic or cloth, it is possible to remove
particles of hair, undissolved dirt and manure, but it must be
remembe