94 BIOLOGY AND TECHNIQUE 



acid upon peroxide of barium. It readily gives up oxygen and acts 

 upon bacteria probably by virtue of the liberation of nascent oxygen. 

 In the presence of organic matter, such as blood, pus, etc., associated 

 with bacteria, H 2 2 is quickly reduced and weakened. It is impor- 

 tant that the H 2 2 come in immediate contact with the bacteria. 

 In practice, therefore, blood and pus should be removed from wounds 

 when applying the H 2 2 or a large excess of H 2 2 should be used. 



PERMANGANATE OP POTASSIUM, acting probably in the same way, 

 is a powerful germicide. It also is readily reduced by many organic 

 substances often associated with bacteria, being rendered weaker 

 thereby. 



Among organic disinfectants those of most practical importance 

 are the alcohols, formaldehyds, iodoform, members of the phenol 

 group and its derivatives, carbolic acid, cresol, lysol, creolin, sali- 

 cylic acid, certain ethereal oils, and, more recently introduced, 

 organic silver salts such as protargol, argyrol, argonin, and others. 



THE ALCOHOLS are but indifferent disinfectants. Koch 40 in 1881 

 found that anthrax spores remained alive for as long as four months 

 when immersed in absolute and in 50 per cent ethyl alcohol. On the 

 other hand, while absolute alcohol possesses practically no germicidal 

 powers, possibly because of the formation of a protecting envelope 

 by the coagulation of the bacterial ectoplasm, or, as suggested above, 

 by desiccation due to the abstraction of water, dilute alcohol in a 

 concentration of about 50 per cent is distinctly germicidal, destroy- 

 ing the vegetative forms of bacteria in from ten to fifteen minutes 

 or less. 41 Attention has already been called to the fact that moderate 

 additions of alcohol to aqueous solutions of mercuric chloride en- 

 hance the germicidal power of this disinfectant. Additions of ethyl 

 and methyl alcohol to carbolic acid or formaldehyde solutions, on 

 the other hand, progressively decrease the bactericidal activities of 

 these substances. 42 



The value of boiling alcohol for the destruction of spores 

 especially in the sterilization of catgut has been investigated by 

 Saul, 43 who found that boiling in absolute ethyl, methyl, or propyl 

 alcohol is practically without effect, while spores are destroyed 



40 Koch, Arb. a. d. kais. Gesundheitsamt, i, 1881. 



41 Epstein, Zeit. f . Hyg., xxiv, 1897. 

 *- Krdnig und Paul, loc. cit. 



43 Saul, Archiv f . klin. Chir., 56, 1898, 



