312 CLEAN MILK 



isolated during these experiments, and as many other kinds of 

 bacteria as may be available. Set all of the tubes aside at 70°, and 

 at intervals of 24 hours examine each to determine the effect upon 

 the milk of the different species of bacteria. The acidity should be 

 tested by removing a loopful and placing on litmus paper, and special 

 attention should be given to curdling, separation of whey, appear- 

 ance of gas bubbles, the digestion of the curd and the appearance of 

 odors as a result of the action of the different bacteria. The larger 

 the variety of the different cultures used, the better. 



