CHEMICAL CRITERIA OF ANAEROBIOSIS 



17 



In the decolorization of methylene blue temperature is a factor; 

 heat plays a double role, driving out oxygen by lowering the 

 solubility point and accelerating the chemical reaction between 

 alkali and organic matter. 



Sunlight also effects the decolorization of methylene blue but 

 this factor is mentioned here only as a disturbing influence which 

 has been avoided in the experimental work. Lasareff (1912) 

 and Gebhard (1912) have shown that the bleaching effect of 

 light is most intense in the absence of oxygen; the color returns 

 in the dark in the presence of oxygen providing exposuce was to 

 wave lengths less than 620 ij.ij. but otherwise does not. 



Table 3 displays the results of an experiment showing that 

 the return of color to decolorized methylene blue agar in bright 

 sunlight is considerably less rapid than in diffuse light or in the 

 dark. 



TABLE 3 



Depth of colored band at top of 2 per cent agar with n JlOO NaOH at different lime 



intervals after decolorization, in varying light intensities 



Sunlight. . . . 

 Diffuse-light 

 Dark 



AFTEB FOLLOWING NUMBER OF MINUTES REMOVAL FROM BATH: 



0.5 

 0.5 

 0.8 



30 



0.6 

 1.1 

 1.5 



45 



1.0 

 2.0 

 2.1 



60 



1.5 

 2.5 

 3.0 



120 



mm. 



2.6 

 3.8 

 4.1 



3.4 

 5.0 

 5.2 



240 



4.1 

 5.5 

 5.6 



300 



4.9 

 6.0 

 6.2 



As to the decolorization of methylene blue by living cells this 

 discussion does not particularly concern itself further than to 

 note with Jordan that "anaerobes will grow in media where 

 . . . . reduced methylene blue shows no trace of reoxida- 

 tion." They will grow also in undecolorized methylene blue 

 but observations of many tests have shown no instance where 

 such growth was unaccompanied by decolorization. While, as 

 Ricketts (1904) has mentioned, we cannot regard the reduction 

 of methylene blue as a definite test for living cells, as Ehrlich 

 and others have suggested, since methylene blue becomes leuco- 

 methylene blue when its affinities for hydrogen have been satis- 

 fied, whether through reduction by living or non living matter. 



