96 BIOLOGY AND TECHNIQUE 



gas and which exerts distinctly bactericidal action on vegetative 

 forms in further dilutions of of from 1 to 10 to 1 to 20 (formaldehyd 

 gas 1 : 400 to 1 : 800). Anthrax spores are killed in 35 per cent 

 formaldehyde in ten to thirty minutes. 48 Unlike the phenols, the 

 addition of salt to formaldehyd solutions does not increase its 

 efficiency, but similar to them, additions of ethyl and methyl alcohol 

 markedly reduce its germicidal powers. 



THE ESSENTIAL OILS which are most commonly used in practice 

 largely as intestinal antiseptics are those of cinnamon, thyme, 

 eucalyptus, and peppermint. Omeltschenko 49 believes that the em- 

 ployment of these oils in emulsions is illogical, inasmuch as their 

 bactericidal powers depend upon their vaporization. He classifies the 

 oils in decreasing order of their efficiency as follows: Oil of cinna- 

 mon, prunol, oil of thyme, oil of peppermint, oil of camphor, and 

 eucalyptol. 



The Flavine Dyes. A number of dye stuffs have been shown to 

 exert disinfectant action when applied to bacteria. The members 

 of the acridine group are particularly active in this respect, and 

 have been used to some extent practically. Benda 50 first investigated 

 one of these dyes, now known under the name of flavine or acri- 

 flavine, in connection with trypanosome infections, and recently 

 Browning 51 applied this substance to the antiseptic treatment of 

 war injuries. 



NH 2 



CH 3 Cl 



Acriflavine. 



He believed that this dye, while being highly toxic to bacteria, was 

 relatively harmless and non-irritating in its effect on the tissue cells. 



48 Kronig und Paul, loe. cit. 



49 Omeltschenko, Cent. f. Bakt., I, ix, 1891. 



50 Benda, Ber. Deutseh. Chem. Gesell, 45, 1787, 1912. 



51 Browning, Gulbsansen, Kennaway and Thornton, Brit. Med. Jour., Jan. 20th, 

 1917. 



