THE DESTRUCTION OF BACTERIA 97 



Practical experience seems to have shown, however, that the healing 

 of wounds that have been treated with acriflavine may be to a certain 

 extent delayed by the action of the dye, which is, therefore, not 

 entirely without effect on tissue cells. Proflavine, a closely related 

 dye, is similar in its effects and less expensive in preparation. 



Triphenylmethane Dyes. Many of the dyes of this series, notably 

 gentian violet, malachite green and brilliant green, have long been 

 known to be highly toxic for bacteria. 



/C 6 H 5 



C^C 6 H 4 =N(CH 3 )2-C1 

 \C 6 H4-N(CH 3 )2 

 Malachite green. 



They are of especial interest since their toxic action seems to be 

 directed almost entirely against Gram-positive bacteria, and some- 

 times a dilution one thousand times or more as strong as is necessary 

 to inhibit the growth of streptococci and staphylococci, will be 

 needed for prevention of growth of the Colon bacillus. Since most 

 of the common pyogenic organisms are Gram-positive, the use of 

 these substances in wound dressings suggests itself. Practically, 

 it has been found, particularly with brilliant green, that, while it 

 acts as a very efficient antiseptic in wounds, here also the dye is 

 not without effect on the tissue cells, and the granulations that are 

 formed in its presence are not of the normal type. Concentrated 

 solutions of crystal violet and brilliant green have been used for 

 sterilizing the skin before operation, and are claimed to be more 

 efficient for this purpose than tincture of iodin. 52 



Methods of Testing the Efficiency of Disinfectants. The effi- 

 ciency of any given disinfectant depends, as we have seen, upon a 

 number of factors, any one of which, if variable, may lead to con- 

 siderable differences in the end result. Thus, as far as the bacteria 

 themselves are concerned, it is necessary to remember that not only 

 do separate species differ in their resistance to disinfectants, but 

 that different strains within the same species may show such varia- 

 tions as well. This fact largely accounts for the widely varying 

 reports made by different investigators as to the resistance of 

 anthrax spores, and depends possibly upon temporary or permanent 

 biological differences produced in bacteria by the conditions of their 

 previous environment. 



* 2 Bonney and Browning, Brit. Med. Jour., May 18th, 1918. 



