CHAPTER V. 

 STERILIZATION AND DISINFECTION. 



BEFORE considering the cultivation of bacteria and 

 the preparation of media for that purpose it is necessary 

 to discuss methods of destroying bacteria whose acci- 

 dental presence might ruin our experiments. 



The dust of the atmosphere, as has already been shown, 

 is almost constant in its micro-organismal contamination, 

 so that the spores of moulds and bacilli, together with 

 yeasts and micrococci, constantly settle from it upon our 

 glassware, enter our pots, kettles, funnels, etc., and would 

 ruin every culture-medium with which we operate did 

 we not take measures for their destruction. 



Micro-organisms may be killed by heat or by the action 

 of chemicals, the processes being generically termed 

 sterilization. The term sterilization is usually employed 

 to denote the destruction of bacteria by heat, in contra- 

 distinction to disinfection, which usually means the 

 destruction of the bacteria by the use of chemical 

 agents. A chemical agent causing the death of bacteria 

 is called a germicide. An object which is entirely free 

 from bacteria and their spores is described as sterile. 

 Certain substances whose action is detrimental to the 

 vitality of bacteria and prevents their growth amid other- 

 wise suitable surroundings are termed antiseptics. 



The study of sterilization, disinfection, and antisepsis 

 will naturally lead us through the following subdivisions : 



I. The sterilization and protection of instruments and 

 glassware used in experimentation. 



II. The sterilization and protection of culture-media. 



III. The disinfection of the instruments, ligatures, etc. 

 and the hands of the surgeon, and the use of antiseptics. 



IV. The disinfection of sick-chambers and their con- 

 tents, as well as the dejecta and discharges of patients 

 suffering from contagious and infectious diseases. 



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