5. Examine each of the culture tubes from day to day, until the completion of seven days, and note those tubes, if any, in which growth takes place. 6. From such tubes as show growth prepare subcultivations upon suitable media, and ascertain that the organism causing the growth is the one originally employed in the test and not an accidental contamination. ~Inferior Lethal Coefficient.~-- _Apparatus Required:_ Highly concentrated solutions of the disinfectants. Sterile test-tubes in which to make dilutions from the concentrated solutions of the disinfectants. Hanging-drop slides. Cover-slips. Erlenmeyer flask containing 100 c.c. sterile distilled water. Case of sterile pipettes, 10 c.c. (in tenths of a cubic centimetre). Case of sterile pipettes, 1 c.c. (in tenths of a cubic centimetre). METHOD.-- 1. Prepare a surface cultivation of the "test" organism B. anthracis upon nutrient agar in a culture bottle and incubate under optimum conditions for twenty-four hours; then examine the cultivation microscopically to determine the absence of spores. 2. Prepare solutions of different percentages of each disinfectant. 3. Make a series of hanging-drop preparations from the agar culture, using a loopful of disinfectant solution of the different percentages to prepare the emulsion on each cover-slip. 4. Examine microscopically and note the strongest solution which does not cause plasmolysis and the weakest solution which does plasmolyse the organism. 5. Make control preparations of these two solutions and determine the percentage to be tested. 6. Pipette 10 c.c. sterile water into the culture bottle and suspend the entire surface growth in it. 7. Transfer the suspension to the Erlenmeyer flask and mix it with the 90 c.c. of sterile water remaining in the flask. 8. Pipette 10 c.c. of the diluted suspension into each of ten sterile test-tubes. 9. Label one of the tubes "Control" and place it in the incubator at 18° C. 10. Add to each of the remaining tubes a sufficient quantity[11] of a concentrated solution of the disinfectant to produce the percentage previously determined upon (_vide_ step 5). 11. Incubate the tubes at 18° C. to 20° C. 12. At hourly intervals remove the control tube and one of the tubes with added disinfectant from the incubator. 13. Make a subcultivation from both the control and the test suspension, upon the surface of nutrient agar; incubate under optimum conditions. 14. Observe these culture tubes from day to day until the completion of seven days, and determine the shortest exposure necessary to cause the death of vegetative forms. ~Superior Lethal Coefficient.~-- 1. Prepare surface cultivations of the "test" organisms upon nutrient agar in a culture bottle, and incubate under optimum conditions, for three days, for the formation of their spores.