LANCET METHOD 147 
120° C.) The tubes were covered with india-rubber caps and kept in 
jars with greased lids to prevent evaporation. 
At the time of the experiment different amounts of a suitable 
dilution of the disinfectant were added to each tube together with 
enough distilled water to make the total volume up to 5 «ec. The 
tubes then contained different concentrations of the disinfectant in 
question in the presence of 3 per cent feces. The tubes were inoculated 
and sampled in exactly the same way as when the test was made in 
distilled water without organic matter. 
Lancet Method. This is a modification of the Rideal-Walker 
method. The following method was advised: 
Bacillus colt commums from a twenty-four hour broth culture 
which had been incubated at 37° C. was used as the test organism. 
The disinfectants were diluted with distilled water and placed in special 
containers 23 by $ ins. Platinum spoons were advised instead of loops 
for the seeding. By this technique more fluid could be carried than 
on any ordinary loop. These spoons carried about 0.08 ¢.c. of water. 
MacConkey’s lactose bile broth was advised for the secondary culture 
tubes. Samples were to be removed every two and a half minutes 
from each container up to fifteen minutes. After this the time interval 
was to be fifteen, twenty, twenty-five and thirty minutes. All tests 
were carried out between 62° and 67° F. The carbolic acid coefficient 
was deduced as follows: ‘‘ The figure representing the percentage 
strength of the weakest lethal dilution of the carbolic acid control was 
divided by the figure representing the percentage strength of the 
weakest lethal dilution of the disinfectant being tested. This was done 
both at the two-and-a-half-minute line and at a thirty-minute line and a 
mean of the resulting figures was taken as the carbolic acid coefficient.”’ 
Determinations of the phenol coefficient have not yielded consistent 
results in the hands of the various investigators. This may not be due 
to the method itself, although it is not perfect in its present technique, 
but to the media used in the various laboratories. Phelps has pointed 
out some of the limitations and Supfle and Dlugeler, Norton, and 
have emphasized the necessity of great care in the preparation of the 
media. The H-ion concentration appears to be very important. De- 
spite these objections, the phenol coefficient is probably the best method 
available at present, for the comparison of the disinfecting properties 
of the coal-tar products. 
