522 -B^ GTERIOL OGY. 



minutes transfer a drop from each tube into a tube of 

 liquefied agar-agar. Pour this immediately into a 

 Petri dish. Label each dish carefully and place them 

 in the incubator. Note the results at the end of twenty- 

 four, forty-eight, and seventy-two hours. How do 

 you explain them ? 



Make identically the same experiment with the same 

 spore-containing culture of anthrax bacilli, except that 

 the drop from the mixture is to be transferred to 10 c.c. 

 of a mixture of equal parts of ammonium sulphide and 

 sterilized distilled water. After remaining in this for 

 about half a minute, a drop is to be transferred to a 

 tube of liquefied agar-agar, poured into Petri dishes, 

 labelled, and placed in the incubator. Note the results. 

 Do they correspond with those obtained in the pre- 

 ceding experiment ? How are the differences ex- 

 plained ? 



Prepare a 1 : 1000 solution of corrosive sublimate. 

 To each of twelve tubes containing exactly 10 c.c. of 

 bouillon add one drop to the first, two drops to the 

 second, and so on until the last tube has had twelve 

 drops added to it. Mix thoroughly and then inoculate 

 each with one wire-loopful of a bouillon culture of 

 staphylococcus pyogenes aureus. Place them all in the 

 incubator after carefully labelling them. Note the order 

 in which growth appears. 



Do the same with anthrax spores, with spores of 

 bacillus suhtilis and with the typhoid bacillus, and see 

 how the results comj^are. From these experiments 

 what will be the strength of corrosive sublimate neces- 



