78 MECHANISM OF DISINFECTION AND HEMOLYSIS 



branch which could be interpreted as a monomolecular curve for the 

 reason that her experiments lasted only a short time." Miss Chick's 

 published curves were, as a matter of fact, time curves, i.e. "integrals" 

 of "mortality" or variation curves, and had she been able to make 

 sufficient observations at the beginning of the process, she might 

 have obtained curves at first horizontal, but very quickly turning 

 downwards. Such a condition would find expression in a mortality 

 curve as an ascending branch rising very steeply from zero to a 

 maximum. 



The true explanation of the course of processes like disinfection is 

 undoubtedly a combination of the two extreme views : one attributing 

 the course to variation alone, the other considering it to express the 

 nature of the fundamental reaction alone. Both of these factors 

 exert an extremely important influence. We have seen that it is 

 theoretically possible to relegate variation to a position of unim- 

 portance by assuming a variation curve having the form y = jn. 

 Such a distribution of various degrees of resistance is obviously 

 unnatural, and the assumption that it occurs must, in the absence of 

 definite evidence, be considered unwarranted. Its use frequently 

 necessitates the postulation of "latent" or "induction" periods of 

 whose existence we have no further proof. On the other hand we 

 may consider the reaction velocity as constant, and by graphic 

 differentiation obtain not unnatural frequency curves. Perhaps by 

 employing several constants we may even obtain applicable equations; 

 but the constants will have no physical meaning, and the equations 

 no general significance. 



The reaction velocity, as a moment's consideration will show, must 

 ordinarily decrease as the process goes on; for "sub-minimal" amounts 

 of the toxic substances carry the process to partial completion, and 

 whatever the final "equilibrium" may be, it is gradually attained; 

 the process does not abruptly cease.^^ 



^" Curves drawn through points expressing the amount of toxic agent required 

 to produce various degrees of completion of such processes might be regarded as 

 "integrals" of the frequency curves of resistance. In practice, however, this 

 reasoning is applicable only to such in vivo experiments as determination of thera- 

 peutic efificiency or toxicity of drugs, radiation, etc. In vitro, factors such as 

 bacterial contamination, autolysis, cell division, or starvation are likely to super- 

 vene, and distort the observed curve. 



