64 BACTERIOLOGY. 



and their spores, that may be within or upon various 

 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. 



In general 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, though for par- 

 ticular purposes such volatile germicides as chloroform 

 and ether may serve as exceptions to this. (See Pres- 

 ervation of Blood-serum with Chloroform, page 90.) 

 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 essential to success that the disinfectant used 

 should come in direct contact with the bacteria to be 

 destroyed, otherwise there is no disinfection. 



For this reason, one should always remember, in 

 selecting the disinfecting agent, the nature of the ma- 

 terials 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 



