THE CHEMISTRY OF LIGHT PRODUCTION 131 



I find that milk is a favorable and convenient medium 

 for the reduction of oxylucif erin and that it acts without 

 the addition of an aldehyde or the presence of bacteria. 

 There is probably a substance acting as the aldehyde in 

 the luciferase-oxyluciferin solution. No light appears if 

 milk is added to a luciferase-oxyluciferin solution, but if 

 the mixture is allowed to stand in absence of oxygen light 

 will appear when air is admitted. The air can be con- 

 veniently kept out by filling small test tubes completely 

 with the solution and closing them with rubber stoppers. 



As almost all animal tissues contain reductases it is 

 not surprising to find that a freshly prepared and filtered 

 extract of Cypridina containing oxyluciferin and luci- 

 ferase, which gives no light on shaking, will, on standing 

 in a stoppered tube for 24 hours at room temperature in 

 the dark give light when air is admitted. While this 

 may be due to the development of bacteria with a reduc- 

 ing action, it does not seem likely, as under the same con- 

 ditions methylene blue is not reduced in 24 hours, and 

 there is no turbidity or smell of decomposition in the 

 tube. In 48 hours bacteria appear and methylene blue 

 is also reduced. If we add chloroform, toluol or thymol 

 to the tubes of Cypridina extract to prevent the growth 

 of bacteria, and allow them to stand 48 hours, upon admit- 

 ting" air the tube with chloroform gives no light but the 

 tubes with toluol and thymol do give light, although it 

 is not so bright as if they were absent. I believe that these 

 substances have a destructive action on the reductases, 

 most complete in the case of chloroform. Dubois (1919 

 c) also has recorded the occurrence of a reducing enzyme 

 in Pholas, a "hydrogenase," which is able to form hydro- 

 gen from cane sugar, and luciferin from a boiled ex- 



