7S BACTERIOLOGY. 



dangerous infective properties without at the same 

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

 latter process depends upon the fact that the vital- 

 ity of many of the less resistant pathogenic organ- 

 isms is easily destroyed by an exposure to particular 

 chemical substances that may be without effect upon 

 the more resistant saprophytes and their spores that are 

 J)resent. 



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 employ- 

 ment is restricted in the laboratory to materials that 

 are of no further value, and to infected articles that are 

 not injured by the action of the agents used, though ex- 

 ceptionally such volatile germicides as chloroform and 

 ether are employed for the sterilization of special culture- 

 media. (See Preservation of Blood-serum with Chloro- 

 form.) In short, they are mainly of value in rendering 

 infected waste-materials innocuous. For the successful 

 performance of this form of disinfection there is one 

 fundamental rule always to be borne in mind, viz., it 

 is 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 mate- 

 rials containing the bacteria u])on 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 insoluble, more or 



