148 



ANTISEPTICS 



tardatioii was the same; the contact of the resting cells 

 with the drug for 3 hours had been without any influence. 

 In another experiment, the bacteria were held without 

 food in presence of sulfonamides for 3 hours at 37°, When 

 the food was added, the culture multiplied normally for 

 a while, thus showing that the delay of the drug effect 

 had not been changed by a 3-hour contact of the culture 

 with the drug, because there had been no growth. Both 

 experiments were made with four different sulfonamides. 

 The authors concluded that ''the interaction between the 

 sulfonamide and the bacterium, therefore, depends upon 

 some reaction associated intimately with growth". 



Another noteworthy difference between sulfonamides 

 and other antiseptics has been pointed out by Kohn and 

 Harris (I.e.). It concerns the relation between con- 

 centration and retardation of growth. Very much more 

 sulfonamide is required to produce strong retardation 

 than slight retardation. Their main data are given in 

 Table 30, together with results obtained by the writer 



TABLE 30 



Retardation of growth of Bacterium colt and of yeast by various 

 antiseptics. 



Antiseptic 



Concentration required to reduce 

 the growth rate 



30% 



85% 



Ratio of the 



two 



concentrations 



Bacterium coli (Kohn and Harris, 1941a) 



Yeast (Rahn, unpublished data) 



Phenol 



Formaldehyde 

 Benzoic acid 



0.10% 



0.003% 



0.015% 



0.17% 



0.007% 



0.040% 



1.7 

 2.3 



2.7 



