HYGIENIC LABORATORY METHOD 155 
Determining the Coefficient. After a large number of experiments 
we have concluded that the method employed by the Lancet commission, 
with certain modifications, is the best one for determining the coeffi- 
cient, 1.e., the mean between the strength and time coefficients. 
In performing the test, plants are made every two and a half minutes 
up to and including fifteen minutes. To determine the coefficient, the 
figure representing the degree of dilution of the weakest strength of the 
disinfectant that kills within two and a half minutes is divided by 
the figure representing the degree of dilution of the weakest strength of 
Fig. 45.—Device for Flaming Inoculating Loops. 
the phenol control that kills within the same time. The same is done for 
the weakest strength that kills in fifteen minutes. The mean of the 
two is the coefficient. The method of determining the coefficient will 
be seen in Table XIII. 
B. THE DETERMINATION OF THE COEFFICIENT WITH THE ADDITION OF 
ORGANIC MATTER 
It may be well to briefly discuss here the meaning or significance 
of the term “‘ phenol coefficient,” particularly when it is determined 
in the presence of organic matter. In general terms the coefficient 
