20 



BACTERIOLOGY FOR NURSES 



Sterilization. — Properly, sterilization means the 

 complete destruction of bacteria, by whatever means; 

 but by custom in the laboratory sterilization is used 

 when heat is the agent employed, and d isinfectj ori^ 

 uaed.Jo--d,esignaig_,siiedii2aJ42JiJ;9t^^ 



Sterilization by heat may be accomplished by dry 

 heat, as by baking or passing an object through a 

 flame, or by moist heat, such 

 as boiUng, or by steam, with or 

 without pressure. Sterilization 

 by heat is commonly employed 

 for the sterilization of utensils, 

 instruments, and culture media, 

 as the action of chemicals 

 would be unfavorable to the 

 cultivation of bacteria; but 

 chemicals are used for disin- 

 fecting the hands, old cultures, 

 and all useless infective materials. 



It is gsti giated that bacte ria and sij ores exposed to. 

 aJesigerature,i2ll70^C:_(338° F.) fOT^pneJiourwilL 

 bg_Qom^etfily^destroyed^ 



There are a number of hot-air sterilizers in com- 

 mon use which give a uniform heat in all parts of 

 the oven. 

 Sterilization by steam under pressure is accom- 



FiG. 5. — Laboratory hot- 

 air sterilizer. 



