Contamination of Milk. 29 



unable to utilize it. Milk sugar, on the other hand, is 

 an excellent food for most species. 



Sources of contamination. Inasmuch as milk is es- 

 pecially exposed to the inroads of bacterial growth, and 

 because of the fact that much of the contamination can 

 easily be prevented, it is highly important that the milk 

 producer and dealer should be thoroughly cognizant of 

 the various sources of contamination. The different fae-. 



FIG. 6. FAT GLOBULES AND BACTERIA. 



Note the relative size of the fat globules of milk and the lactic 

 acid bacteria. 



tors concerned in contamination may be grouped as fol- 

 lows: the interior of the udder; utensils, including all 

 apparatus with which the milk is brought in contact sub- 

 sequent to withdrawal from the animal; infection com- 

 ing from the animal herself, from the milker, and the 

 surrounding air. 



Condition of milk when secreted. Immediately after 

 withdrawal from the udder, milk always contains bac- 



