STERILIZATION AND DISINFECTION. gl 



materials and objects, i. e., to sterilize them ; and it is 

 also possible by the same means to rob infected objects 

 of their dangerous infective properties without at the 

 same time sterilizing them — i. e., to disinfect them. 

 This latter process depends upon the fact that the 

 vitality of many of the less resistant pathogenic organ- 

 isms is easily destroyed by an exposure to particular 

 chemical substances, while a similar exposure may be 

 without effect upon the more resistant saprophytes and 

 their spores that are present. 



The use of chemicals for sterilization is not to be 

 considered in connection with substances that are to be 

 employed as culture media, and their employment is 

 restricted in the laboratory to materials that are of no 

 further value and to infected articles that are not in- 

 jured by the action of the agents used. In short, they 

 are mainly of value in rendering infected waste materials 

 free from danger. For the successful performance of 

 this form of disinfection there is one fundamental rule 

 always to be borne in mind, viz., it is absolutely essen- 

 tial to success that the disinfectant used should come in 

 direct contact with the bacteria to be destroyed, other- 

 wise there is no disinfection. 



For this reason, one should always remember, in 

 selecting the disinfecting agent, the nature of the 

 materials containing the bacteria upon which it is to 

 act, for the majority of disinfectants, and particularly 

 those of an inorganic nature, vary in the degree of 

 their potency with the chemical nature of the mass to 

 which they are applied. Often the materials containing 

 the bacteria to be destroyed are of such a character that 

 they combine with the disinfecting agent to form insol- 

 uble precipitates ; these so interfere with the penetration 



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