62 DISINFECTANTS 



ter is concentrated; propionic acid will prevent the 

 growth of molds, but not of bacteria; sulfa compounds 

 work well internally, but are poor disinfectants in vitro. 



We shall use in this discussion the customary distinc- 

 tion between disinfectants (called also germicides or bac- 

 tericides) and antiseptics, though the line of demarca- 

 tion between them is not sharp. According to the gen- 

 eral conception, disinfectants sterilize, i.e., they kill all 

 bacteria present, whereas antiseptics merely prevent 

 their multiplication. Disinfection is something final, 

 irrevocable, while antisepsis is something temporary 

 which can be interrupted or discontinued by the removal 

 of the antiseptic. 



This definition would imply, if taken literally, that 

 antiseptics never cause death. However, most anti- 

 septics kill at least a small percentage of cells per hour, 

 yet death is always very slow, so that even after several 

 days not all cells are killed. Thus a precise distinction 

 between disinfectants and antiseptics is possible only 

 by choosing an arbitrary time limit, and by specifying 

 various conditions (see below, pp. 63 and 118). 



Though these specifications are arbitrary, there is 

 clearly a fundamental difference between the tempo- 

 rary, reversible inhibition assumed in the definition of 

 antiseptics and the permanent, irreversible inhibition 

 required in that of disinfectants. In some cases, as 

 with crystal violet, it has been proved experimentally 

 that the chemical reaction causing reversible inhibition 

 is different from that which causes irreversible inhibi- 

 tion, as will be seen below (p. 136). 



