S. C. BROOKS 77 



Yule's formulas lead to a "monomolecular" curve. It seems more 

 rational to adopt some explanation which takes into account the 

 individual variations in resistance, thus avoiding unnatural assump- 

 tions as to the nature of the fundamental reaction. 



IV. 



The idea that the rate of disinfection is due to variations in resist- 

 ance is not new; Geppert^'' gave expression to it nearly a generation 

 ago. The same idea has since been restated in many forms and in 

 many connections, but always without reference to any influence 

 which might be exerted by the fundamental reaction. 



Mioni ''i'22 criticizes Henri's studies^^ on hemolysis, because Henri 

 neglected the influence of individual variation; Mioni's experimental 

 evidence is inconclusive, however. Dienes^^ suggested that various 

 degrees of resistance to hemolysis were distributed in accordance with 

 "Quetelet's law" (3^ = 3^0 e~^^) . Hewlett^^ says, with reference to the 

 hypothesis offered by Miss Chick in her first paper, "While admitting 

 that the disinfection of anthrax spores follows the course of a unimo- 

 lecular reaction, I think it extremely doubtful, to say the least, if the 

 reaction between disinfectant and bacterium is a unimolecular reac- 

 tion." Hewlett's own experiments on the effect of mercuric chloride 

 on the viability of mustard seeds accord with those of Darwin and 

 Blackman,^'' but he says: "It appears to me that only by a wide stretch 

 of the imagination can the interaction of mustard seed and disinfect- 

 ant be considered as a unimolecular reaction, or a reaction of a higher 

 order, yet it follows approximately the course of the former." 



Loeb and Northrop^^ also criticize the idea that disinfection is 

 due to a monomolecular reaction. They say Miss Chick "was 

 probably led to such an assumption by the fact that the ascend- 

 ing branch of the mortality curve in her experiments was generally 

 very steep .... almost a vertical line, thus escaping 

 detection. Hence she noticed usually only the less steep descending 



20 Geppert, J., Bed. klin. Woch., 1889, xxvi, 789. 



21 Mioni, G., Ann. Inst. Pasteur, 1905, xix, 84. 



22 Mioni, Compt. rend. Soc. bioL, 1905, Ivii, 485. 



23 Hewlett, R. T., Lancet, 1909, i, 889. 



2" Loeb, J., and Northrop, J. H., /. Biol. Chem., 1917, xxxii, 103. 



