282 



MILK 



is largely soil, the count will be much smaller in proportion to the 

 actual number present than- if manure is the chief contaminating 

 substance. The extensive use of clarifiers also tends to reduce 

 the amount of dirt present without materially decreasing the germ 

 content. 



It has been shown by Esten and Mason that the dust which 

 accumulates on poorly cared for cows is very rich in bacteria. One 

 gram of curry powder from a cow contained 207,000,000 bacteria, 

 while one gram of curry powder from a horse had 18,000,000. 

 The dust drops from the animal at every move and contaminates 

 the stable air. Whether bacteria multiply on the skin of the 



Fig. 89. A barn with filthy surroundings. (Webster, Bull. No. 56, 

 Hygienic Laboratory.) 



cow is not definitely known, but it does not seem unlikely that 

 some kinds may do so. Food for bacteria is present in the 

 form of organic matter, chiefly manure, and sometimes sufficient 

 moisture may be present, although the cow's skin does not per- 

 spire (Figs. 89-91). 



Esten and Mason think that the cow is the most prolific source 

 of bacteria in milk, and state that the udder furnishes 4 per cent, 

 and the surface of the animal 70 per cent, of all bacteria in milk, 

 and that the balance of 26 per cent, comes from all other sources 

 combined. Some investigators, as we shall see, do not agree 

 with this estimate, but there can be no doubt that in the last 

 analysis the surface of the cow harbors the bacteria that later 



