140 
BACTERIA IN MILK. 
The exterior of the cow is an even more prolific source than the 
milk ducts. 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, 
FIG. 29. A cow's udder cut across and showing the milk ducts. 
if ever, cleaned; her flanks, tail, and skin become covered with a coat- 
ing of manure, until the amount of filth thus attached to the animal is 
surprisingly great. All of this filth is laden with bacteria, and 
during the milking process numerous particles of it are constantly 
