18 



BULLETIN 303, U. S. DEPARTMENT OF AGRICULTURE. 



In order to test the value of this medium as compared with the bile 

 tube method, 43 samples of ice cream were examined. The results 

 are shown in Table 11. It may be seen that the colon count as deter- 

 mined on litmus-lactose-asparagin agar was higher than the number 

 estimated from bile tubes in 41 of 43 samples. In most samples the 

 number determined from the asparagin plates was much higher; in 

 one sample it was 47 times as high as the number calculated from 

 bile tubes. 



Table 11. — Comparison of the number of Bacillus coli in ice cream determined by the 

 bile-tube method and on litmus-lactose-asparagin-agar plates. 





Bile 

 medium. 



Litmus-lactose-asparagin-agar plates. 



d 

 to 



1 



m 



Bile 

 medium. 



Litmus-lactose-asparagin-agar plates. 



6 



1 

 03 



m 



B. coli. 



B. coli. 



Cul- 

 tures 

 picked. 



Cultures 



picked 



which 



form gas 



in lactose 



broth. 



Per cent 



gas 

 formers. 



B. coli. 



B. coli. 



Cul- 

 tures 

 picked. 



Cultures 



picked 



which 



form gas 



in lactose 



broth. 



Per cent 



gas 

 formers. 



1 





15,400 



86,000 



200 



100 



8,000 



900 



2,500 



13,000 



2,900 



5,600 



7,200 



400 



12, 000 



11,900 



123, 000 



3,000 



3,900 



39, 000 



5,000 



2,400 



7,700 



2,400 



154 

 80 



146 



78 



94.80 

 97.50 



23 

 24 

 25 

 26 

 27 

 28 

 29 

 30 

 ' 31 

 32 

 33 

 34 

 35 

 36 

 37 

 38 

 39 

 40 

 41 

 42 

 43 



5,000 



50,000 



5,000 



100,000 



100, 000 



1,000 



250 



1,000 



100 



2,500 



500 



500 



250 



75 



1,000 



250 



75 



50 



75 



100 



750 



108, 000 



120, 000 



75,000 



300, 000 



600, 000 



47, 000 



5,600 



6,500 



1,200 



15,000 



3,000 



3,000 



1,730 



550 



2,530 



2,350 



20 



(2)0 



100 

 230 

 820 









?, 











3 



50 



(i)0 



500 



500 



1,000 



5,000 



750 



2,500 



1,000 



250 



1,000 



2,500 



7,500 



75 



50 



750 



250 



750 



1,000 



250 









4 



1 



8 



9 



22 



12 



29 



53 



62 



4 



12 



86 



91 



3 



39 



38 



5 



1 



8 



9 

 22 

 12 

 29 

 51 

 57 



4 

 11 

 80 

 85 



3 

 34 

 38 



5 



100.00 

 100.00 

 100. 00 

 100. 00 

 100. 00 . 

 100. 00 

 98.01 

 91.93 

 100.00 

 91.61 

 93.02 

 93.29 

 100. 00 

 87.17 

 100.00 

 100. 00 









5 









6 









7 









8 









9 









in 









n 









n 









13 









14 









15 









16 









17 









18 









19 









?n 









?i 















?? 































1 In tto 



dilution. 







2] 



n y^ dilu 



Jon. 







