EXPERIMENTS 323 



and at the end of five minutes transfer a drop from each tube 

 to tubes of liquefied agar-agar. Pour these immediately into 

 Petri dishes. 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 preceding experiment? How are the differences 

 explained? 



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 micrococcus 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 

 subtilis, and with the typhoid bacillus, and compare the 

 results. From these experiments, what will be the strength 

 of corrosive sublimate necessary to antisepsis under these 

 conditions for the organisms employed? 



Make a similar series of experiments using a 5 per cent, 

 solution of carbolic acid. 



