266 



ESSENTIALS OF BACTERIOLOGY 



One- tenth of a cubic centimeter of the culture is 

 added to 5 c.c. of the disinfectant dilution. The phenol 

 control is made of different dilutions, from 5 to 10 strengths 

 being employed. The disinfectant to be tested is likewise 

 diluted, depending on the solubility, etc. An accurately 

 graduated pipet distributes y 1 ^ c.c. of the culture to each 

 one of the dilutions, both of the phenol control and the test, 

 and the tubes are then shaken gently three times. At 

 intervals of two and one-half minutes a platinum loopful 

 (the loop 4 mm. in diameter) is transferred from each tube 

 and planted in the tube of broth medium. The inoculated 

 tubes are then placed in an incubator at 37 C. for forty- 

 eight hours, and at the end of this time results are recorded. 



The coefficient is determined and recorded as in the ex- 

 ample here given. 



EXAMPLE. 



Name of disinfectant to be tested, A. 

 Temperature, 20 C. 



Culture used, Bacillus typhosus, o.i c.c. to 5 c.c. disin- 

 fectant. 



The weakest disinfectant dilution that kills within tw r o and 

 one-half minutes (1-375) is divided by the weakest phenol 



