224 



NINETEENTH REPORT. 



Laboratory formulated a third method which seems to be the most satis- 

 factory of any yet worked out. The Hygienic Laboratory method, as it 

 is called, is essentially the method employed by the Lancet Commission 

 with certain modifications. In this method the organism used is B. 

 typhosus, a twenty-four hour culture in a beef extract broth showing a 

 reaction to phenolphthalein of -|- 15 Fuller's scale. The cells are ex- 

 posed to the action of the properly diluted disinfectant to be tested and 

 of the phenol control. Plantings of the exposed organisms are made in 

 standard beef extract broth every two and one-half minutes up to and 

 including 15 minutes. A standard temperature of 20° C. is adopted for 

 the experiment, and is maintained by a properly regulated water bath. 

 To determine the phenol coefficient "the figure representing the degree 

 of dilution of the weakest strength of the disinfectant that kills within 

 two and one-half minutes is divided by the figure representing the degree 

 of dilution of the weakest strength of the plienol control that kills within 

 the same time. The same is done for the weakest strength that kills 

 witliin 15 minutes. The mean of the two is the coefficient." This method 

 of determining the coefficient is taken in Table 2 taken from Anderson 

 and McClintic. 



Table No. 2. 



Name, "A." 



Temperature of medication, 20° C. 



Culture used, B. typhosus, 2 i-hour, extract broth, filtered. 



Proportion of culture and disinfectant, 0.1 cc. -\- 5 cc. 



— — 2 



Phenol 

 coefficient. 



375 



80 



4- 



650 

 10 = 



4.69 + 5.91 = 

 2 

 5.30 



Consideration of the various methods for the laboratory determina- 

 tion of the fungicidal value of various fungicides and the germicidal 

 value of disinfectants seemed to indicate that a method somewhat similar 



