580 



S. HENRY AYERS AND COURTLAND S. MUDGE 



TABLE 2 

 Bacterial counts on milk-powder agar A and B compared with extract agar and 



infusion agar 



EXTRACT AGAR, 



STANDARD 



METHODS 



A. P. H. A. 1916 



INFUSION AGAR, 



STANDARD 



METHODS 



A. P. H. A. 1910 



INCREASE 

 OVER EX- 

 TRACT AGAR 



MILK-POWDER 

 AGAR B (0.2 PER 

 CENT PEPTONE), 



(0.1 PER CENT 

 MEW EXTRACT) 



INCREASE 

 OVER 



EXTRACT 

 AGAR 



MILK-POWDER 

 AGAR A, (0.5 PER 

 CENT PEPTONE), 



(0.3 PER CENT 

 MEAT EXTRACT) 



INCREA8E 



OVER 



EXTRACT 



AGAR 



Raw milk 



Pasteurized milk 



Certified milk 



4,100 

 4,900 



7,600 

 5,700 



85.0 

 16.3 



6,500 

 6,500 



58 

 32 



6,200 

 5,200 



51 

 6 



This milk-powder agar "B" does not give quite such char- 

 acteristic pictures with different samples of milk as does the first 

 mentioned milk-powder agar "A." However, it is a clear medium 

 and is cheaper than medium "A." 



MILK-POWDER YEAST AGAR 



It is sometimes said that it is impossible to expect uniformity 

 in bacteria counts as long as peptone and meat extract are so 

 variable. Of course every one will agree that different makes 



