TESTING DISINFECTANTS II3 



EXERCISE LVIII 



TESTING DISINFECTANTS (Continued) 



168. Work for this Exercise — Prepare two sets of tubes, 

 each containing 10 c.c. of a 2.5, i.o, and 0.5% solution, re- 

 spectively, of carbolic acid and test their effect upon the organ- 

 isms used in the last exercise and by the same method. Note 

 the conditions of the inoculated tubes at the next exereise. 



Examine and describe the appearance of the tubes inoculated 

 during the preceding exercise. 



Allow the inoculated tubes to remain in the incubator for 

 several days and note whether or not any of them develop 

 after the first 24 hours. If they do, examine them micro- 

 scopically to .determine if the culture is pure. Observe in 

 these cultures the difference between immediate destruction 

 and the retarding of the growth of the bacteria. 



