588 S. HENRY AYERS AND COURTLAND S. MUDGE 



more closely related to the actual number of bacteria in the milk; 

 secondly, they give different "pictures" when different samples 

 of milk are plated; and, thirdly, this is accomplished without 

 any significant increase in expense. In fact, one of these media 

 is much cheaper than extract agar. All the milk-powder media 

 are very much cheaper than the old standard infusion agar. 



6. The full value of these milk-powder agar media can be 

 determined only by the results obtained from the analysis of 

 a large number of samples of milk. While our experiments are 

 extensive, we realize that they only indicate the probable value 

 of the media. 



REFERENCES 



Ayers, S. Henry Casein media adapted to bacterial examination of milk. 



28th Ann. Rpt. Bur. Animal Industry, 225-229. 

 Ayers, S. Henry, and Rupp, Philip 1920 Extracts of pure dry yeast for 



culture media. Jour. Bact., 5, 89-98. 

 Sherman, James M. 1916 The advantage of a carbohydrate medium in the 



routine bacterial examination of milk. Jour. Bact., 1, 481-488. 



