56 



LAWRENCE T. FAIRHALL AND PAUL M. BATES 



The method of determining sterility adopted in the earlier 

 part of this work, i.e., emulsifying the oil directly with beef in- 

 fusion agar and plating, is open to the objection that incomplete 

 contact is secured between the oil and the agar, so that no 



Fig. 1 



growth is not conclusive proof of sterility. As a consequence, a 

 method which gives a far more accurate index of sterility was 

 adopted. This consists in shaking samples of the oil with sterile 

 beef broth contained in small glass bottles together with a few 

 glass beads and incubating for twenty-four hours. At the end 



