xiv BACTERIAL POLLUTION OF MILK 239 



Add 1 c.c. dilution D to each of 4 L.B.B. tubes. 

 C 4 



B 1 



- * i* 



Incubate all 10 tubes for two days at 37 C. and record 

 as for byre milk. In summer the L.B.B. tube inoculated 

 from dilution A may usually be safely omitted. 



Using this method of examination results much less spaced 

 than with the usual dilutions with 0*1, O'Ol, O'OOl c.c., etc., 

 of milk can be obtained, while in actual working the ex- 

 amination is very simple. For byre milk samples, the seven 

 L.B.B. tubes can be at once prepared from the milk with the 

 one pipette, and the results read off after two days' incubation. 

 For vended milk samples, the dilutions would have to be pre- 

 pared with one 10 c.c. pipette, and then the ten L.B.B. tubes 

 inoculated, and the results read off after two days' incubation. 



The interpretation of the results appears perhaps somewhat 

 complicated, but the following explains how they should be 

 interpreted. 



Byre samples. The possible variations are : 



Vended milk samples. 



( 4 positive 

 D | 3 

 tubes I : " 



C 



tubes 



B 



tube 



A 

 tube 







= over 10,000 

 = 7500-10,000 

 -5000-7500 

 = 2500-5000 

 = less than 2500 

 = 1000 or more 

 = 750-1000 

 = 500-750 

 = 250-500 

 = less than 250 

 = 100 or more 

 = less than 100 

 = 10 or more 

 = less than 10 



per 

 c.c. 



