242 



BACTERIOLOGICAL METHODS 



tubes. After making the plants, the loops or spoons are flamed a: 

 already described. 



After an experiment is finished the date and any necessary 

 details can be marked on one of the broth tubes and the racl 

 placed in the incubator at 37 C. for 48 hr. At the end of thi 

 time the results are recorded on a chart especially devised for thi 

 purpose. (See Table III.) 



Determining the Coefficient. After a large number of experi 

 ments, we have concluded that the method employed by the Lance 



FIG. 87. Device for holding and flaming inoculating loops. (Anderson & McClintic 

 Hygiene Laboratory Bulletin No. 82, U. S. Public Health Service.) 



Commission, with certain modifications, is the best one for de 

 termining the coefficient, i.e., the mean between the strength am 

 time coefficients. 



In performing the test, plants are made every 2}^ min. up t< 

 and including 15 min. To determine the coefficient, the figur< 

 representing the degree of dilution of the weakest strength of th< 

 disinfectant that kills within 2% min. is divided by the figun 



