570 APPLICATION OF METHODS OF BACTERIOLOGY 



means to influence in any way the production of spores by 

 the organism with which you are working. What is the 

 effect, if any? 



Prepare two bouillon cultures, each from one drop of 

 blood of an animal dead of anthrax. (Why from the blood 

 of an animal and not from a culture?) Allow one of them 

 to grow for from fourteen to eighteen hours in the incubator; 

 allow the other to grow at the same temperature for three 

 or four days. Remove the first tube after the time men- 

 tioned and subject it to a temperature of 80° C. for thirty 

 minutes. At the end of this time prepare four plates from 

 it. Make each plate with one drop from the heated bouillon 

 culture. At the end of three or four days treat the second 

 tube in identically the same way. How do the number of 

 colonies which develop from the two cultures compare? 

 Was there any difference in the time required for their 

 development on the plates? 



From a potato culture of bacterium anthracis which has 

 been in the incubator for three or four days scrape away 

 the growth and carefully break it up in 10 c.c. of sterilized 

 physiological salt-solution. The more thoroughly it is 

 broken up the more accurate will be the results of the 

 experiment. Place this in a bath of boiling water, and at 

 the end of one, three, five, seven, and ten minutes make 

 plates upon agar-agar each with one loopful of the contents 

 of this tube. Are the results on the plates alike? 



Determine the exact time necessary to sterilize objects, 

 such as silk or cotton threads, on which anthrax spores have 

 been dried, by the steam method and by the hot-air method. 



