134 THE NATURE OF ANIMAL LIGHT 



or Al is placed in water. "With Mg the water becomes 

 only slightly alkaline from formation of almost insoluble 

 Mg(OH)o. If we add some Al powder and dilute NaOH 

 to an oxyluciferin solution, H is given off and luciferin 

 is formed. As oxyluciferin cannot be formed by the addi- 

 tion of alkali alone we must have in this experiment a 

 reduction of oxyluciferin in a,Ikaliae medium by the nas- 

 cent H produced. Luciferin can also be formed by merely 

 adding Al or Zn or Mg dust to an oxyluciferin solution. 

 Methylene blue can also be readily reduced to its leuco- 

 base by Zn dust or Al -f NaOH. 



Indeed, if one adds some Al or Zn or Mg powder to a 

 solution of lucif erase, light will appear whenever the solu- 

 tion is shaken. Luciferase solution must always contain 

 the oxidation product of luciferin, oxyluciferin. In pres- 

 ence of nascent H this is reduced to luciferia, and siuce 

 the reaction of the medium is alkaline and luciferase is 

 present this is oxidized with light production, when, by 

 shaking, air is dissolved. The light can never become 

 very bright except at the surface because of the deficiency 

 of oxygen in the solution. It would seem, then, that the 

 action of bacteria, yeast, muscle cells, etc., on oxyluciferin 

 must be due not entirely to their acid reaction but to 

 their reducing power as well. * 



The above experiment is a very striking and instructive 

 one. Given a test tube of luciferase solution containing, 

 as it does, oxyluciferin, add some Zn dust or Mg powder, 

 and the evolution of hydrogen begins. Conditions are now 

 favorable for the reduction of oxyluciferin and this occurs. 

 Shake the contents of the tube to dissolve oxygen and light 

 appears. AUow the tube to stand and the light soon dis- 

 appears. Shake again and the light reappears. The lumi- 



