MICRO-ORGANISMS IN MILK 281 



fiers (Figs. 86-88), the soluble portion remains. Aside from the 

 addition of bacteria chiefly of the fecal type, including gas formers, 

 from this source, the very presence of fecal matter is highly objec- 

 tionable from an esthetic point of view. 



Fig. 88. — Simplex centrifugal milk clarifier. 



The absence of a definite relation of insoluble dirt to the germ 

 content of milk is shown by the following work of Uhl: 



RELATION OF INSOLUBLE DIRT TO GERM CONTENT OF MILK 



Number. Mgrs. dirt per liter. Number of bacteria per cubic centimeter. 



1 3.68 12,897,000 



2 2.53 36,690,606 Each number 



3 2 07 7,099,820 represents the 



4 1.55 55,365,800 average of five 



5 1.17 3,831,460 samples. 



6 0.52 3,338,775 



The writer in an examination of Chicago market milk also 

 could detect no definite relation between insoluble dirt and bac- 

 terial numbers, while Ayers, Cook, and Clemmens found that 

 the sediment test bears a "somewhat close relation to the number 

 of bacteria in fresh, unstrained milk handled in sterilized utensils." 



It should be considered, however, that all kinds of dirt 

 do not carry the same number of bacteria. One kind con- 

 tains much greater germ life than another, so that the source 

 of the dirt has a substantial influence on the number of 

 germs that are carried with it into the milk. Furthermore, 

 many bacteria are not taken into account because they do 

 not grow on ordinary culture-media. If the dirt, for example, 



