Methods of Sterilization 



203 



I. The Sterilization and Protection of Instruments 

 and Glassware. Sterilization may be accomplished by 

 either moist or dry heat. For the perfect sterilization of 

 objects capable of withstanding it dry heat is always to be 

 preferred, because of its more certain action. If we knew 

 just what organisms we had to deal with, we might be able 

 in many cases to save time and gas ; but though some non- 

 spore-producing forms are killed at a temperature of 60 C., 



pig 3 g Hot-air sterilizer. The gas jets are inclosed within the 

 space between the outer and middle walls, C, and can be seen at F. 

 The heat ascends, warming the air between the two Inner walls, which 

 ascends between the walls, K, then descends over the contents, /, and 

 escapes through perforations in the bottom, B, to supply the draft at 

 F, and eventually escapes again at S; R, gas regulator; T, thermometer. 



spore-bearers may withstand 100 C for an hour; it is, 

 therefore, best to employ a temperature high enough to kill 

 all with certainty. The sterilizing apparatus, or "hot-air 

 sterilizer," is shown in Fig. 38. 



Platinum wires used for inoculation are sterilized by being 

 held in the direct flame until they become incandescent. 



