170 LABORATORY EXERCISES IN BACTERIOLOGY. 



Note difference in the cultures at close of first, second, and third days. To 

 what group is the organism to be referred from its optimum temperature ? 



Exercise 37. From a known culture of Bacillus tetani a stab culture in 

 agar is made (glucose agar if preferred). It is placed for forty-eight hours 

 in the incubator. Does development occur? 



It is now transferred to anaerobic jar in an atmosphere of hydrogen and 

 again placed in the incubator, and observed for the usual time. To what 

 class of bacteria does this germ belong from its relations to free air access ? 



Exercise 38. Two tubes of agar are inoculated by stroke from a known 

 culture of Bacillus typhosus. One is placed in the anaerobic jar in an at- 

 mosphere of hydrogen, the other retained in the air. Both are placed in 

 the incubator. Note the results of growth at the close of the first, second, 

 and third days. To what group does this organism belong from its relation 

 to air? 



Exercise 39. From a known culture of Pseudomonas pyocyanea (Bacil- 

 lus pyocyaneus) make a stroke inoculation on a tube of agar. Place in an 

 atmosphere of hydrogen for two days at incubator temperature. Does 

 growth occur? Transfer the tube to the open air in the incubator. Ob- 

 serve the results after one, two, and three days. Is this organism an 

 obligate anaerobe, facultative anaerobe, or obligate aerobe? 



Exercise 40. One or two loopfuls of fresh pus are diffused in a few cubic 

 centimeters of sterile water. Smear preparations are made on two agar 

 ' 'slants" (tubes in which the medium has been solidified in slanting position). 

 One is placed in the sunlight near the window, the other in a dark place at 

 the temperature of the room. Compare the two tubes each day for three 

 days and note results. Can the culture exposed to sunlight be developed 

 by transfer to darkness and warmth, or are its organisms dead? 



