172 CONCLUSIONS 



8. The efficiency of antiseptics cannot be studied by 

 the technique used with disinfectants. As the reaction 

 of antiseptics is instantaneous, no rate of reaction can 

 be computed, and the mode of action can be ascertained 

 only by observing the effects of weaker doses which re- 

 tard, but do not stop multiplication. No temperature 

 coefficient and no concentration exponent can be estab- 

 lished for antiseptics. 



9. Antiseptics retard multiplication in two quite dif- 

 ferent ways; they may decrease the multiplication rate, 

 or they may increase the lag period, i.e., the time normal- 

 ly required by transferred cells to adjust themselves to 

 the new environment, or to change from the senile to the 

 juvenile state. Dilute phenol, penicillin, and sulfon- 

 amides decrease the reproduction rate without affecting 

 the lag period. Dyes extend the lag period, eventually 

 to several days, without reducing the rate of reproduction, 

 if multiplication starts at all. Formaldehyde, sulfur diox- 

 ide and benzoic acid prolong the lag phase and also re- 

 duce the rate of multiplication. 



10. As was said above, the lethal reaction of most dis- 

 infectants is a reaction with some molecule without which 

 cell division cannot take place. It seems certain that this 

 molecule must be of protein nature. No other single 

 molecule can be so important. The compounds causing 

 death belong to a great variety of chemical groups, and 

 do not react in the same way with proteins. But a native 

 protein has many very different sidechains, and the inac- 

 tivation of any one of these may be sufficient to terminate 

 its physiological function. Thus the fundamental lethal 

 reaction of different disinfectants may not be identically 

 the same, but it represents an attack on the same mole- 

 cule, or group of molecules. Exceptions must be ex- 

 pected. Chlorine has already been mentioned as attack- 

 ing first the cell membrane. It is imaginable that some 

 compounds destroj^ the enzymes more readily than the 

 synthesis or multiplication mechanisms, though all evi- 



