SOURCES OF MILK BACTERIA I5r 
possible. Therefore, it is a matter of much importance to learn 
the sources from which these milk bacteria are derived. Knowl- 
edge upon this point will enable the dairyman to adopt precau- 
tions in the production and caring for the milk that will materially 
reduce their number. A shght attention given at the right point 
will produce better results than a much greater attention unin- 
telligently applied. 
The Cow.—The first source of milk bacteria is the cow. Al- 
though the healthy cow may secrete milk in a sterile condition, 
it is never sterile when it leaves the milk duct. There are always 
some bacteria in the ducts ready to be washed into the milking 
pail with the first jet of milk. At the close of the milking enough 
milk is left in the ducts to furnish food for bacteria, which may 
get in through the external opening; and between the milkings, at 
the warm temperature of the cow’s body, these bacteria multiply 
(Fig. 28). Bacteria are thus always abundant near the opening 
of the teat, although the inner parts of the duct contain smaller 
numbers. They are sure to contaminate the first jets of milk 
drawn, so that this first lot, called fore milk, always contains 
more bacteria than that drawn later in the milking. When a 
cow’s udder is diseased (garget) or merely inflamed the streptococci 
discharged with the milk are very numerous. Sometimes the 
milk from one such cow, when mixed with the milk of other cows, 
will cause the mixed milk to contain a hundred thousand or more 
bacteria per c.c. 
The exterior of the cow is another possible source of bacteria. 
Her skin, even when kept in fairly good condition, is never very 
clean, and will always hold more or less dirt and dust laden with 
bacteria. The cow in many poorly kept dairies is rarely, if ever, 
cleaned; her flanks, tail, and skin may become covered with a 
coating of manure, until the amount of filth thus attached to the 
animalis surprisingly great. All of this filth is laden with bacteria, 
and during the milking process numerous particles of it are con- 
stantly shed from her body by the movements of her flanks, by 
