24 IVAN C. HALL 



on methylene blue we have to recognize that both adsorption 

 and reduction are concerned. 



To complete a representative study of porous substances used 

 in the cultivation of anaerobic organisms I have selected white 

 sea sand. There has been a strong suggestion in such recent 

 work as that of Douglas, Fleming and Colebrook (1917) that 

 the principal value in plant and animal tissues added to culture 

 media for the cultivation of obligative anaerobes lies in their 

 provision of interstices which by their minute size serve to prevent 

 diffusion of oxygen as well as to afford secluded foci for the initi- 

 ation of growth, and this view has much to commend it. They 

 have shown, indeed, and others as well as ourselves have con- 

 firmed, the value of various inert insoluble substances added to 

 media in place of animal and plant tissue. 



When I attempted the treatment of simple methylene blue 

 solutions with sand, results startlingly like those with tissues 

 were secured except that there was no reduction in the depths 

 of the sand. In brief, adsorption is the sole process concerned 

 here, and it occurs aerobically as well as anaerobically. In a 

 Smith fermentation tube filled with an aqueous methylene blue 

 solution and shaken up with sand which settled into the neck, 

 marked decolorization occurred in both the open and the closed 

 arms. 



Of course it was impossible to "extract" a reducing agent from 

 sand. But so far as the solution itself was concerned it behaved 

 exactly like that treated with tissue; with this exception, that 

 some reducing agent such as glucose, as well as an alkaline 

 reaction had to be provided in order to secure complete decolori- 

 zation by heating. 



Whereas sand of itself has no true reducing action, there is no 

 doubt of its efficacy as a means of maintaining reduced oxygen 

 pressure, as we may judge from the persistence for many days 

 of decolorization in the closed arm of a fermentation tube pro- 

 vided with a slightly alkaline glucose solution of methylene blue 

 and a sand seal in the neck of the tube. The sand seal with 

 suitable culture media in the fermentation tube is also quite 

 satisfactory from the cultural standpoint. 



