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STERILIZATION. 6 1 



CHAPTER II. 



STERILIZATION. 



BY sterilization is meant the killing of all microorgan- 

 isms found on or in any body or substance. It is possible 

 to sterilize objects by the use of bichloride of mercury (cor- 

 rosive sublimate), carbolic acid and other chemical agents. 

 Sterilization is usually accomplished by heat. The most 

 effective sterilization is that done by steam and by borling; 

 they are not, however, suitable for all kinds of material. 



The naked flame of the Bunsen burner or the alcohol 

 lamp is used largely for the sterilization of small articles. 

 It is evident that no more efficient way of sterilization could 

 be devised than by burning objects, or subjecting them to 

 a red heat. The uses of this method will at once suggest 

 themselves; for instance, surgical dressings that have be- 

 come soiled with discharges and similar materials can be 

 most easily disposed of by simply burning them up. In 

 laboratory work the flame is constantly employed for the 

 sterilization of the platinum wire, forceps, pipettes and 

 cover-glasses; occasionally test-tubes are sterilized in this 

 manner. 



Hot-Air Sterilization. Hot air, at a temperature of 150 

 C, or higher, maintained for an hour, is very valuable for 

 some materials although less effective than steam. It has 

 been found that the spores of certain bacteria are not killed 

 even by exposure to this temperature, but it is sufficient for 

 ordinary conditions. Hot-air sterilization is employed for 

 glassware such as Petri dishes, flasks and test-tubes. 

 Flasks and test-tubes are generally plugged with raw cot- 



