MECHANISM OF DEATH 355 



more or less efficient the disinfectant under test was than phenol 

 (see Table 111). 



This comparison was inaccurate. On account of the differences in 

 the concentration exponent n, two disinfectants having equal power 

 at a certain concentration may vary widely if they are both diluted 

 at the same ratio (see Fig. 39). Chick (1908) brought out this point 

 very strongly by showing that the phenol coefficient was a function 

 of the killing time, as is shown in the data of Table 112. 



As a result of these investigations, all modern methods of com- 

 paring disinfectants including the Rideal-Walker test have standard- 

 ized the time in which the organisms must be killed. This is of 

 limited value only, however, since the phenol coefficient holds true 

 only for the time set in the experiment, e.g. ten minutes with Bad. 

 coll, and gives not even an approximate conception of the concentra- 

 tion required to kill in thirty minutes or in five minutes. The choice 

 of phenol as the standard was especially unlucky since it has the 

 highest concentration coefficient of all disinfectants. 



If we realize further, that the selection properties of bacteria 

 interfere, and that we obtain different phenol coefficients with differ- 

 ent bacteria (see p. 346), there seems to be little left to rely upon in 

 the Rideal-Walker test. But no better or more practical method 

 has so far been suggested for standardization. About the various 

 kinds of phenol coefficients, their history, their virtues and objections, 

 and the factors influencing their accuracy, see Tanner and Wallace 

 (1929). 



(e) THE MECHANISM OF POISONING 



A very thorough attempt to obtain a knowledge of 

 the mechanism of poisonous action was made by Reichel 

 (1909) . He measured the distribution of phenol between 

 oil and water, and the influence of salt upon this partition 

 (Fig. 40), demonstrating that addition of salt increases 

 the phenol concentration in the oil. The same experi- 

 ment was then repeated with coagulated albumin instead 

 of oil, and the same relation was found to take place. 

 The ratio of phenol in the solid albumin phase and in 

 the watery phase was plainly that of a partition by 

 physical solubiUties, and not of adsorption or chemical 



