210 



Dairy Bacteriology. 



1. Dirt or sediment test. This is made by filtering a 

 pint of the mixed milk through a small disc of absorbent 



FIG. 39. SEDIMENT TESTERS. 



In the use of the apparatus on the right, increased air pres- 

 sure is used to hasten the filtering process; the same is ac- 

 complished in the apparatus shown in the center by warming 

 ing the milk by the injection of steam between the walls of 

 the double jacket. 



cotton. The insoluble dirt is retained and imparts a 

 color to the cotton, the shade of which is dependent on 

 the amount of dirt (P. 45) . Since it is impossible to have 

 dirt without bacteria, it is evident that milks containing 



