120 ANTISEPTICS 



actions produced by the same toxic agent lias already 

 been given in the experiments by Gegenbauer with mer- 

 curic chloride. The inhibition of growth of staphylococci 

 could be reversed during the first hour of exposure by re- 

 peated washing, but after longer exposure, even an anti- 

 dote would not restore the ability to multiply. Another 

 example in which antisepsis and disinfection effects have 

 been measured separately will be found later in the dis- 

 cussion of crystal violet. 



Antiseptics cannot be studied in the same way as dis- 

 infectants because with them there is no measurable rate 

 of reaction, no death rate and no death time. The in- 

 stantaneous reaction is followed by a period of no fur- 

 ther change in the status of antisepsis. Even if some or 

 all cells slowly die, that does not affect the status of 

 antisepsis, for the dead cells continue not to multiply, just 

 as the living cells do not multiply. The exceptional 

 case of the sulfa drugs which permit a short period of 

 apparently normal growth before the status of antisepsis 

 becomes established will be treated in a separate chapter. 



An antiseptic is characterized by the lowest concen- 

 tration which will inhibit multiplication. Higher con- 

 centrations produce no effect different from that of the 

 sufficient concentration. Since little can be concluded 

 from the knowledge of only the inhibiting concentra- 

 tion, the effect of more dilute solutions is also studied. 

 Such solutions are not truly antiseptic, but important 

 conclusions can be dra\vn from their effect on the rate of 

 multiplication, the length of the Jag period, and the final 

 crop. The rate of multiplication is usually retarded, the 

 lag period is greatly prolonged by some antiseptics, but 

 not changed at all by others, and the final crop usually 

 decreases as the antiseptic concentration increases. This 

 latter effect is well illustrated by the following data on 



