THE CHEMISTRY OF LIGHT PRODUCTION 135 



nescence reduction and oxidation process can be demon- 

 strated many times. 



A similar experiment can be performed with lucif erase 

 and oxylucif erin solution by addition of NH4SH. This will 

 serve also as another example of the reduction of oxyluci- 

 f erin in an alkaline medium. Whenever we shake a tube 

 of luciferase, oxyluciferin and NH4SH, light will appear. 

 When the tube is at rest it becomes dark. Even the merest 

 touch is sufficient to agitate the tube contents, cause solu- 

 tion of oxygen and appearance of light. It is just as if we 

 stimulate the tube to produce light and I believe the phe- 

 nomenon has a deeper significance and a more fundamen- 

 tal similarity to the phenomena of stimulation than may 

 at' first appear. What more simple means of controlling 

 a process can we think of than by admission or with- 

 drawal of oxygen? The firefly turns on its light by 

 stimulation through nerves of the luminous organ. Nocti- 

 luca flashes on stimulation of any kind, even the slightest 

 agitation causing a brilliant emission of light. If the 

 stimulation process means merely the admission of oxygen 

 to the photogenic cells we have a mechanism in the cell 

 itself for automatically producing the light. The admis- 

 sion of oxygen results in aerobic conditions and lucif erin in 

 presence of luciferase can then oxidize to oxyluciferin with 

 luminescence. When the oxygen is used up, the light 

 ceases, anaerobic conditions prevail, and the oxyluciferin 

 is reduced to lucif erin again. Thus, lucif erin is reformed 

 during the rest period of Noctihica or between the flashes 

 of the firefly. What more efficient type of light than this 

 is to be desired? 



Again, methylene blue offers an interesting parallel to 

 oxyluciferin. A little NH4SH added to methylene blue 

 10 



