MICRO-ORGANISMS IN MILK 



279 



matter to determine the exact amount of foreign matter that is 

 actually present in milk, and modern methods take account only 

 of the insoluble portion of dirt (Fig. 85). Esten and Mason state 

 that three-quarters of cow manure is soluble, but this varies with 



the consistency of the feces. However, a considerable portion of 

 cow manure is insoluble, and consequently unclean milk, as a 

 rule, contains more or less of this disgusting material. Even 

 though the insoluble dirt is removed by modern centrifugal clari- 



