4 IVAN C. HALL 



cator of anaerobiosis by Smith (1893) and others, it has been used 

 to a certain extent by ahnost every serious investigator of anaero- 

 biosis since. Smith (1893) (1896) noted its decolorization in the 

 closed arm of the fermentation tube. SanfeHce (1893) and 

 Liefmann (1908) defended the use of glass sHps on the basis of 

 the decolorization of methylene blue in the underlying agar. 

 Trenkmann (1898) and Rivas (1902) used it in their culture tests 

 with Na2S as a reducing agent. Kabrhel (1899) used it in his 

 bell jar device for plates and thereby showed the necessity of 

 removing the covers for efficacious absorption of oxygen by 

 alkaline pyrogallol; he also showed its value as an indicator of 

 the anaerobiosis of deep culture media, liquid and solid. It 

 was used by Petri (1900) in connection with oxygen tension 

 reduction by hydrogen and alkaUne pyrogallol, by Sellards (1904) 

 with phosphorus, by FremUn (1903) (1904), Stuler (1904), 

 Berner (1904), Lentz (1910) with various plating devices, by 

 Wrzosek (1907) (1909), Liefmann (1907), Hata (1908), Guil- 

 lemot and Szczawinska (1908), Zinsser, Hopkins and Gilbert 

 (1915) with plant and animal tissues, by Laidlaw (1915), and 

 Mcintosh and Fildes (1916) in the use of spongy platinimi and 

 palladium black as hydrogen-oxygen catalysers, by Wilson (1917) 

 in the use of coal gas, by Douglas, Fleming, and Colebrook (1917) 

 in connection with many porous substances and by a great many 

 others. 



CHEMISTRY OF METHYLENE BLUE 



Discovered by Caro in 1876 and used empirically for many 

 years in the arts, methylene blue, as a chemical compound, was 

 studied most authoritatively by Bernthsen. He showed (1883) 

 that Na2S204 reduces it to its colorless leuco base, methylene 

 white, which may be crystallized out of ether and whose aqueous 

 solution becomes dark blue again in acid solution with iron 

 chloride. Mohlau (1883) expressed the rule that methylene 

 white is changed to methylene blue by oxidizing agents in acid 

 solution. Bernthsen (1883) engaged in a brief polemic with 

 Mohlau (1883) and Erlenmeyer (1883) as to the structural 

 formulae of these compounds and finally (1884) set down meth- 

 ylene blue chloride as 



