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every particle of dirt, whether it seems to the eye a source of con- 
tamination or not, carries with it great numbers of bacteria, and that 
milk at ordinary temperatures, 65° F. to 100° F., is an excellent 
medium for their growth, and most of the changes that take place 
in milk can be traced directly to such action. 
Neither straining nor clarifying will remove the bacteria from the 
milk, hence the necessity of keeping the dirt out, not straining it out. 
SOURCES OF CONTAMINATION. 
From the act of milking to the final consumption of the milk the 
possibilities of contamination are many and varied in character. 
Everything that comes in direct contact with the milk may be a 
source of trouble, and many things may act indirectly and seriously 
affect the results desired. 
MILKING. 
The first contamination usually begins with the act of milking. 
If the udder and flanks of the cow are covered with the dirt of the 
yard or stable the process of milking will dislodge a greater or less 
portion of this filth, causing it to fall into the pail. 
The amount of filth that may be on a cow will depend very much 
on the condition of the stable yard, and floor, gutter, and bedding 
in the stables. 
The following illustrations are used to better show conditions 
which are too common the country over. The condition of the cow 
shown in Fig. 29 is not exaggerated. The milker is probably all 
unconscious that he is sowing the seeds of contamination and destruc- 
tion, which may sooner or later cause the death of infants who are 
unfortunate enough to be fed from milk produced under such cir- 
cumstances. If he is aware of this fact he is criminal in purpose 
and intent, and the most stringent penalties should be provided to 
stop such work. Figs. 31, 32, 33, and 34 show exteriors and interiors 
of barns which will contribute to such a fearful condition. 
As to the amount of filth that will get into the milk and the result 
on the product, reports from the Illinois Experiment Station and 
Storrs (Conn.) Experiment Station are here quoted: 
The average weight of dirt which falls from muddy udders during milking 
is 90 times as great as that which falls from the same udders after washing, 
and when udders are slightly soiled it is 32 times as great. (Bulletin No. 84, 
Illinois Experiment Station.) 
Wiping the flank and udder of the cow with a damp cloth just before milk- 
ing is a very efficient method for reducing the number of bacteria which falls 
into the milk pail. (Stocking. — Bulletin No. 42, Storrs Experiment Station.) 
