22 IVAN C. HALL 



edly bluer on exposure, and if cut into displayed a decreasing 

 intensity of dye in the interior, the color deepening rapidly in 

 contact with the ah. Such an experiment may be interpreted 

 as indicating adsorption plus reduction, the latter occurring 

 mainly, if not exclusively, within the plant tissue. 



Acid (n/100 HCl) and alkaline (n/100 NaOH) solutions gave 

 similar results. Heating such a series immediately in the boiling 

 water bath resulted in decolorization of the alkaline solution 

 only. Exposed to the air in the tube the color returned to this 

 solution on cooUng in an intensity practically equal to that of 

 the neutral and acid solutions. Adsorption proceeded in all 

 three and did not seem to be notably accelerated by the heat- 

 ing. Previous boiling of the potato fragment seemed to have 

 no influence on the result. 



Extraction by boiling a 1 gram fragment of potato in 1.0 cc. 

 of n/10 HCl, neutral water, or n/10 NaOH for ten minutes and 

 decanting the supernatant fluid yielded a solution containing a 

 reducing substance for methylene blue which could be demon- 

 strated by its decolorization on boiling in n/20 alkahne solution. 

 The color readily returned to such solutions on exposure to the 

 air in a Petri dish. The method of extraction suggested that 

 the substance extracted was probably starch which assumption 

 was substantiated by the iodine test. Starch reduces methylene 

 blue on boiling in alkaline solutions. 



Experiments with animal tissues, such as rabbit and guinea 

 pig liver, in aqueous solutions of methylene blue gave results 

 apparently identical with those recorded for plant, i.e., potato 

 tissues. The solutions, acid, neutral and alkaline, became 

 decolorized in the immediate neighborhood of the tissues within 

 a few hours and almost completely, throughout, in twenty-four 

 hours. The nearty colorless solutions separated from their tis- 

 sues did not regain their color on exposure to the air nor could 

 they be completely decolorized by heating except in the case of 

 the alkahne solution. Alkalinization of the neutral and acid 

 solutions, however, facilitated their rapid decolorization by heat. 

 The tissues became slightly tinged with blue during contact with 

 the dye solution and quickly colored on exposure to the air, 



