CHEMICAL CRITERIA OF ANAEROBIOSIS 23 



both on the surface and in the exposed depths. These phenom- 

 ena coincide exactly with those observed for the plant tissue 

 and point to the same two processes, adsorption and reduction. 



But when it came to extraction of the reducing substance from 

 the annual tissues it was found that the solutions from freshly 

 boiled liver, whether acid (n/10 HCl), neutral, or alkaline (n/10 

 NaOH) , failed to decolorize methylene blue added to them, even 

 when strongly alkalinized and heated further. Immediate 

 decolorization upon the addition of a trace of glucose proved 

 the suitability of the general conditions of the test for the proof 

 of a reducing agent. But kept in the ice chest overnight either 

 with or without previous boiling, and in acid, neutral or alkaline 

 solutions and then further boiled immediately previous to sepa- 

 ration of the clear supernantant fluids, guinea-pig liver yielded 

 a reducing substance to the fluid capable of decolorizing meth- 

 ylene blue under the influence of heat in alkaline solutions. 

 Guinea pig kidney also gave a similar result in neutral distilled 

 water; acid and alkaline extractions of kidney were not tried. 



The results with these animal tissues differ from those wuth 

 potato, both in respect to the relative ease of extraction of the 

 reducing agent in the latter case, and probably in regard to its 

 chemical natm-e. There is little reason to doubt that the reduc- 

 ing substance extracted from potato is starch; the chemical 

 nature of that from the animal tissues is only conjectural. We 

 maj-- say definite^ that it belongs to the non-heat-coagulable 

 extractives, that it is not materially affected by relatively strong 

 acids and alkalis, and that it escapes from the tissue into the 

 solution during sixteen hours maceration in the ice chest or at 

 room temperature, with or without previous boiling. Further- 

 more, and this may be the point overlooked by Zinsser, Hopkins 

 and Gilbert (1915), a necessary condition for decolorization of 

 methylene blue by heat in the presence of either the reducing 

 substance from potato or that from rabbit and guinea pig liver 

 and kidney is an alkaline reaction. Solutions so decolorized 

 regain their color on exposure to air. 



Thus in considering the action of such plant and animal tissues 

 in anaerobic culture media from the standpoint of their effect 



