6 GENERAL MICROBIOLOGY 



III. Sterilization by Dry Heat. 



1. Sterilization in a naked flame. 



2. Sterilization in an ether flame. 



3. Sterilization in a muffle furnace. 



4. Sterilization by hot air. 



1. Sterilization in a Naked Flame, (a) The simplest 

 means of sterilizing a metal instrument is to heat it to red- 

 ness in a flame. This method is always adopted for ster- 

 ilizing platinum, copper, etc., wires and iron and nickel 

 spatulas, forceps, etc. 



A platinum needle should always be carefully dried 

 before sterilization, by holding it near the flame. This 

 avoids sputtering, which scatters microorganisms, especially 

 if moist material, e.g., fat or protein, on the needle is 

 immediately thrust into the flame. 



(6) An instrument may be sterilized by flaming it, 

 i.e., by passing it rapidly through a hot flame. This method 

 is useful for instruments, etc., having polished surfaces 

 devoid of creases in which microorganisms might escape 

 destruction, e.g., knives, glass rods, handles of platinum 

 needles, mouths of test tubes, flasks, pipettes, etc. 



(c) Deep wounds are sterilized by cautery with an 

 instrument heated to a dull red heat. 



2. Sterilization in an Ether Flame. In an emergency, 

 small instruments, needles, etc., may be sterilized by dip- 

 ping them in ether or absolute alcohol and after removal 

 lighting the adherent fluid and allowing it to burn off the 

 surface of the instruments. Repeat the process. It may 

 then be safely assumed that the apparatus so treated is 

 sterile. 



3. Sterilization in a Muffle Furnace. Porcelain filter 

 candles are sterilized by heating them to white heat in 

 the muffle furnace. This method of sterilization cannot 

 be applied to porcelain filters with metal fittings, such as 

 Berkefeld filters. 



The destruction of autopsied animals and accumulated 



