84 DISINFECTANTS 



though they cannot multiply in acid media, such as cider, 

 are however not killed, and start to multiply as soon as 

 the acid is neutralized. (The production of this type of 

 ''suspended animation" is usually called antisepsis.) The 

 antidote does more than washing or diluting, it repairs 

 the primary injury done by the disinfectant to the cell 

 mechanism, but not the further injury resulting from the 

 abnormal or interrupted functioning of the injured mech- 

 anism. When this secondary injury has advanced so 

 far as to be irreparable, the cells cannot be revived by 

 the antidote. 



The application of disinfectants to wounds must be 

 considered from this viewpoint. It has been shown that 

 bacteria, affected chemically to the point where they 

 cannot multiply in broth, may still cause infection when 

 injected in animals. The rapid circulation of liquids in 

 the body results in a washing of the bacteria. Besides, 

 certain compounds of the blood or tissue juices may 

 diffuse into the bacterial cell and react chemically with 

 the disinfectant therein. 



VI. PROPERTIES OF VARIOUS GROUPS OF DISINFECTANTS 



It is not our purpose in this discussion to describe the 

 effect of each bactericide, or the advantages and disad- 

 vantages of its use in various applications. Such de- 

 scriptions will be found in medical handbooks (see, for 

 example, "Disinfection and Sterilisation" by McCul- 

 loch). We are concerned here mainly with the nature 

 of the lethal reaction. 



1. Acids. Strong mineral acids act essentially by 

 their hydrogen ions. Kronig and Paul demonstrated this 

 in their classical study on the physical chemistry of dis- 

 infection (1897), in which they found that most of the 

 strong acids kill bacteria at approximately the same 

 rate when diluted to the same normality. (Since many 



