S. C. BROOKS 73 



comparable to a molecule. For this reason Robertson^^ has offered 

 another explanation for the apparent exponential decrease in the 

 number of surviving cells ; i.e., for the apparent applicabihty of the 

 law of monomolecular reactions. His explanation assumes the colli- 

 sions with the disinfectant molecules to be distributed fortuitously 

 among the different individuals of a homogeneous group of cells. 

 Since it would be out of place to consider here the details of his 

 mathematical proof, it must suffice to point out that Robertson's 

 quantity x, "the number of units of the underlying change," must 

 apparently be at one and the same time a constant, and an expo- 

 nential function of time. This impossible assumption is the basis of 

 Robertson's whole proof. Other mathematical inconsistencies occur, 

 but are of relatively little consequence. 



In a subsequent paper*^ Miss Chick modifies her original theory 

 by assuming that it is the protein molecules of the bacterial proto- 

 plasm, which, like the sugar molecules during hydrolysis, undergo 

 the cyclic changes in energy content, upon which depend their ability 

 to react. The concentration of these protein molecules at any moment 

 would then, according to Miss Chick, determine the rate of death of 

 the bacteria at that moment. We have already seen that under these 

 conditions the cells of a group of uniformly resistant individuals, such 

 as Miss Chick postulates, would all die at one time. If the course of 

 disinfection is to parallel that of the reaction, the diametrically oppo- 

 site condition must prevail; namely, one in which the cells are equally 

 distributed among all the possible classes of resistance; in other words, 

 the equation of the variation curve must he y = yo- 



Von Liebermann and von Fenyvessy^^ explained the hemolytic 

 "monomolecular curve" on the basis of the probable rate of exit of 

 hemoglobin from the individual cell, from which the pigment might 

 be supposed to diffuse at a rate proportional to the difference between 

 the intra- and extracellular hemoglobin concentrations. This explan- 

 ation is evidently in conflict with the observed progressive decrease in 

 the number of intact erythrocytes, and with the fact reported by 

 Dienes^^ that there is a nearly constant ratio between the hemoglobin 



1^ Robertson, T. B., /. Hyg., 1914, xiv, 143. 

 ^* Dienes, L., Biochem. Z., 1911, xxxiii, 268. 



