136 THE NATURE OF ANIMAL LIGHT 



solution will reduce (decolorize) it to the leuco-base. If 

 the tube is now shaken the blue color returns. On standing 

 reduction again occurs. The process can be repeated a 

 number of times, the reaction going in one or the other 

 direction, depending on the oxygen content of the mixture. 

 As methylene blue contains no oxygen, its reduction 

 consists in the addition of two atoms of hydrogen. When 

 leuco-methylene blue oxidizes, water is formed by the 

 union of these two atoms of hydrogen with oxygen, thus : 



Ci6 H20 N3 SCI + O ^ C16 H18 N3 SCI + H2O 

 (leuco-meth3'lene blue) (methylene blue) 



Briefly - MH2 + O ^ M + H2 O 



To reduce methylene blue we can add the two hydrogen 

 atoms directly from nascent hydrogen formed in the solu- 

 tion or we can split up water by a catalyzer in the pres- 

 ence of some substance, which will take up the oxygen of 

 water, thus : 



Na H2 PO2 + H2 O + Pd = Na H2 PO3 + H2 + Pd 



(Sodium h>pophospliite) (Sodium phospbite) 



This reaction occurs in j)resence of fmely divided 

 palladium. Methylene blue can be reduced by the Ho 

 and the hypophosphite oxidized. 



Since oxyluciferin can be reduced by palladium and 

 sodium hypophosphite (Harvej^, 1918), it is probable that 

 we can write the equation for reduction of oxyluciferin and 

 oxidation of luciferin in a similar manner to that of 

 methylene blue : 



Luciferin + O ^ Oxyluciferin -f- H2O 



Briefly - LHo 4- O ^ L + H2O. 



Just as in the case of methylene blue the reaction pro- 

 ceeds in the right hand direction spontaneously if the 



