FROM THE PRACTICAL VIEWPOINT 



easy to say whether the machine, its operation, or 

 the milk is at fault. 



In regard to the milk itself, there are many fac- 

 tors which must be taken into account when de- 

 termining the efficiency of any apparatus. Esti- 

 mates of machine efficiency based upon the 

 percentage of bacteria destroyed are frequently 

 misleading. It can be readily seen that if the bac- 

 terial content of the raw milk is high, any good 

 pasteurizer will kill a large percentage of the 

 germs in the milk. For instance, if the original 

 milk contained 5,000,000 bacteria per c.c., and 

 after being pasteurized contains 100,000 bacteria, 

 there would have been a reduction of 98 per cent, 

 of the bacteria in the original milk. Milk contain- 

 ing 100,000 bacteria per c.c. would not, however, 

 be considered to be an entirely satisfactory prod- 

 uct to place upon the market, especially if it con- 

 tained organisms of the coli type. 



Again, let us suppose that the original milk con- 

 tained 10,000 per c.c., and that by means of the 

 pasteurizing process this number was reduced to 

 1,000; such a milk would undoubtedly be a proper 

 milk for consumption, although the percentage of 

 reduction had been QO per cent only. It is there- 



187 



