LOGARITHMIC ORDER OF DEATH 31 



Explanations of the Logarithmic 

 Order. The striking difference between the mortality 

 curves of bacteria and those of higher organisms has at- 

 tracted the attention of many biologists. According to 

 their attitude towards this problem, they can be divided 

 into three groups. The first group denies the existence 

 of a logarithmic order of death. They maintain that 

 bacteria have the same type of survivor curve as higher 

 organisms, but that the rapidity of bacterial death makes 

 us overlook a first period of low mortality, which, though 

 very short, would nevertheless be present. The second 

 group accepts the logarithmic order as an experimental 

 fact and claims that it is brought about by an unusual 

 distribution of bacterial resistance; various biological 

 reasons for this peculiar gradation of resistance are of- 

 fered. The third group believes that variation in re- 

 sistance is a minor issue, and that the logarithmic order 

 must be explained by analogy to the monomolecular re- 

 actions of chemistry. 



The attitude of the first group can be characterized by 

 the following quotation from Loeb and Northrop (1917) : 

 ''Miss Chick states that ... in each interval of time the 

 same percentage of individuals alive at this time is 

 killed. She was probably led to this assumption by the 

 fact that the ascending branch of the mortality curve in 

 her experiments was generally very steep. The agencies 

 used by her for killing the bacteria were so powerful that 

 the ascending branch became almost a vertical line, thus 

 escaping attention. Hence she noticed usually only the 

 less steep descending branch which could be interpreted 

 as a monomolecular curve for the reason that her exper- 

 iments lasted only a short time." 



Knaysi (1930, 1-V) took up this general line of thought 

 in five short papers. We are primarily concerned here 

 with his experiments with weak disinfectants (paper II) 

 which show a very slow decrease in the number of or- 

 ganisms for the first two minutes, and which resulted in 



