THE COLON GROUP OF BACILLI lS9d 



common carriers in interstate commerce. (Public 

 Health Reports, XXIX, 2959, Nov. 6, 1914.) 



"The following are the maximmn limits of permis- 

 sible bacteriological impurity: 



"i. The total number of bacteria developing on 

 standard agar plates, incubated 24 hours at 37 degrees 

 C, shall not exceed 100 per cubic centimeter, provided 

 that the estimate shall be made from not less than 

 two plates, showing such numbers and distribution 

 of colonies as to indicate that the estimate is reliable 

 and accurate. 



"2. Not more than one out of five lo-c.c. portions 

 of any sample examined shall show the presence of 

 organisms of the baciUus coU group when tested as 

 follows: 



"(a) Five lo-c.c. portions of each sample tested shall 

 be planted, each in a fermentation tube containing not 

 less than 30 c.c. of lactose peptone broth. These shall 

 be incubated 48 hours at 36 degrees C. and observed 

 to note gas formation. 



"(6) From each tube showing gas, more than 5 per 

 cent of the closed arm of fermentation tube, plates 

 shall be made after 48 hours' incubation, upon lactose 

 litmus agar or Endo's medium. 



"(c) When plate colonies resembling B. coU develop 

 upon either of these plate media within 24 hours, a 

 well-isolated characteristic colony shall be fished and 

 transplanted into a lactose-broth fermentation tube, 

 which shaU be incubated at 37 degrees C. for 48 

 hours. 



"For the purposes of enforcing any regulations which 



