342 APPLICATION OF METHODS OF BACTERIOLOGY 



Determine the antiseptic value of the common disinfec- 

 tants for the organisms with which you are working. 



Determine the time necessary for the destruction of the 

 organisms with which you are working, by corrosive sub- 

 limate in 1 : 1000 solution, under different conditions with 

 and without the presence of albuminous bodies other than 

 the bacteria, and under varying conditions of temperature. 



In making these experiments be careful to guard against 

 the introduction of sufficient sublimate into the agar-agar 

 with which the Petri plate is to be made to inhibit the growth 

 of the organisms which may not have been destroyed by 

 the sublimate. This may be done by transferring two drops 

 from the mixture of sublimate and organism into not less 

 than 10 c.c. of sterilized physiological salt solution, in which 

 they may be thoroughly shaken for from one to two minutes, 

 or into the solution of ammonium sulphide of the strength 

 given. 



To 10 c.c. of a bouillon culture of micrococcw aureus or 

 anthrax spores add 10 c.c. of a 1 : 500 solution of corrosive 

 sublimate, and allow it to remain in contact with the 

 organisms for only one-half the time necessary to destroy 

 them (use an organism for which this has been determined). 

 Then transfer a drop of the mixture to each of three liquefied 

 agar-agar tubes and pour them into Petri dishes. Place 

 them in the incubator and observe them for twenty-four, 

 forty-eight, and seventy-two hours. No growth occurs. 

 How is this to be accounted for? 



At the end of seventy-two hours inoculate all of these 

 plates with a culture of the same organism which has not 

 been exposed to sublimate, by taking up bits of culture on 



