682 
J. A. REPLOGLE. 
the number of germs exposed to the disinfectant nor the num¬ 
ber that survive its action. 
Second : By use of fluid cultures. This method was used 
by Geppert and Schafer; but as it did not give satisfaction, soon 
gave way to the exact dilution method, to be described later. 
In this method, equal quantities of dilute and more con¬ 
centrated solutions of the disinfectant are put in a number of 
sterilized tubes. With a sterilized dropping pipet, an equal 
number of drops of a well-shaken culture is added to each of 
the tubes, and mixed with its contents by gently shaking. 
The same number of drops of the same culture that is added 
to the disinfectant solution, is added to a tube of sterilized 
bouillon for the control tube. 
A large number of tubes with 5 to 10 cc. of nutrient jelly 
or agar in each are kept at a liquefying temperature. From 
each of the disinfectant solutions containing the organisms, 
as well as from the control tube, one drop is transferred to 
one of the nutrient jelly or agar tubes, and the tubes placed 
in the thermostat. The same dropper being used in all to in¬ 
sure the transfer of about the same quantity in each one. 
The objection to this method is that too much of the dis¬ 
infectant may be transferred to the nutrient media with the 
organisms, and thus prevent the germ from growing when it 
is not destroyed and thus lead to deception. 
In my experiments with carbolic acid, 1 have employed 
the exact dilution method, described by A. C. Abbot in the 
Johns-Hopkins Hospital Bulletin, in his article on corrosive 
sublimate, of which 1 will give a description. 
Fluid cultures, or watery suspensions of the organisms were 
mixed with carbolic acid solutions in such proportions that 
the organisms were in a fluid containing the acid in the re¬ 
quired proportion, 2: 100, ij: 100 or 1:100 as the experiments 
will show. 
This was done by adding to 23.5 cc. of distilled sterilized 
water .5 cc. of acid ; this was thoroughly shaken and allowed 
to stand until the acid was dissolved ; then 1 cc. of bouillon 
culture of the organisms was added, and gently shaken to dis¬ 
tribute the germs through the solution. 
