s in which very satisfactory results have been obtained. If the
rubber parts of the milker are thoroughly cleaned and kept in lime water
solution, they remain nearly sterile. When milk is properly handled, the
germ content may be greatly reduced.

~Reduction in dirt and adherent bacteria.~ No factor of contamination is
so susceptible of improvement as that which relates to the reduction in
filth and dirt which gains access during and immediately subsequent to
the milking. The care which is taken to keep the coat of the animal
clean by grooming lessens very much the grosser portion of such
contamination, but with a dry, hairy coat, fine scales and dust
particles must of necessity be dislodged.[28] Ordinarily the patron
thinks all evidence of such dirt is removed if the milk is strained, but
this process only lessens the difficulty; it does not overcome it.
Various methods are in use, the effectiveness of which is subject to
considerable variation. Some of these look to the elimination of the
bacteria after they are once introduced into the milk; others to the
prevention of infection in the first place.

_1. Straining the milk._ Most of the visible, solid particles of filth,
such as hairs, dirt particles, etc., can be removed by simple straining,
the time-honored process of purification. As ordinarily carried out,
this process often contributes to instead of diminishing the germ life
in milk. The strainer cloths unless washed and thoroughly sterilized by
boiling harbor multitudes of organisms from day to day and may thus
actually add to the organisms present. Various methods have been
suggested for this simple process, but the most practical and efficient
strainer is that made of fine wire gauze to which is added 3-4 layers of
cheese cloth, the whole to set over the storage milk can.

_2. Filtration._ In Europe especially, the system of cleaning milk by
filtration through sand, gravel and other substances has been quite
extensively used. These filters are built in sections and the milk
passes from below upward. The filtering substance is washed in hot water
immediately after use and then steamed and finally baked. While it is
possible to remove the solid impurities in this way, the germ content
cannot be greatly reduced.[29] Cellulose filters have also been
suggested[30] as an improvement over the sand filters. Methods of
filtration of this character have not been used under commercial
conditions here in this country.