EXPERIMENTS. 523 



sary to act as an antiseptic under these conditions for 

 the organisms employed ? 



Make a similar series of experiments, using a 5 per 

 cent, solution of carbolic acid. 



Determine the antiseptic point of the common disin- 

 fectants for the organisms with which you are working. 



Determine the time necessary for the destruction of 

 the organisms with which you are working, by corro- 

 sive sublimate in 1 : 1000 solution, under different con- 

 ditions with and without the presence of albuminous 

 bodies other than the bacteria, and under varying con- 

 ditions of temperature. 



In making these experiments be careful to guard 

 against the introduction of enough sublimate into the 

 agar-agar from 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 thor- 

 oughly 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 staphylococcus 

 pyogenes aureus, or anthrax spores, add 10 c.c. of cor- 

 rosive sublimate in 1 : 500 solution, and allow it to re- 

 main in contact with the organisms for only one-haty 

 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- 



