288 STUDIES ON BIOLUMINESCENCE. XIV 



covered by Dubois^ in Pyrophorus, an elaterid beetle, and Pholas, a 

 mollusk can be demonstrated in several other groups of the animal 

 kingdom but not in all. Why cannot these substances be demonstrated 

 in all orders? It would seem that so fundamental a reaction should 

 be universal; that is one question awaiting solution. 



A second question concerns the specificity of luciferin and luci- 

 ferase. Will the luciferase of one species produce light with the 

 luciferin of another species, or genus, or group, and vice versa? We 

 have here material for an interesting study of enzyme specificity and 

 this is necessary, as we shall see, for a proper analysis of the first 

 question, why luciferin and luciferase cannot be demonstrated in all 

 groups of luminous animals. 



The Luciferin-Lucif erase Reaction. 



The general methods for preparing luciferin and luciferase are very 

 simple. Luciferin is made by adding hot water to the luminous organ 

 of the animal or by quickly heating the luminescent extract of the 

 luminous animal to temperatures which permanently quench the 

 light, or to boiling. By this means the luciferase is destroyed on 

 heating before the luciferin (which is not destroyed by heating) has 

 been completely oxidized. Care must be taken to destroy the luci- 

 ferase as quickly as possible, before it has had time to oxidize the 

 luciferin. Hence the advantage of adding hot water suddenly to 

 the luminous gland. Care must also be taken not to heat the luci- 

 ferin to too high a temperature, or too long, as it may be destroyed 

 under these conditions. Hence the advantage of heating a luminous 

 extract to just the point where the light is permanently extinguished, 

 and cooling quickly. Before deciding that luciferin cannot be demon- 

 strated in an animal, these precautions have always been taken. 



Luciferase is prepared by allowing a cold water extract of the 

 luminous gland to stand until the luciferin has been completely oxi- 

 dized. This oxidation can be accelerated by shaking the solution to 

 aerate it well, or by gentle heating (not sufficient to destroy the luci- 

 ferase), or by adding such substances as chloroform, saponin, or 

 sodium glycocholate. These substances apparently act by Uberating 



1 Dubois, R., Compt. Rend. Soc. Biol, 1885, ii, 559; 1887, iv, 564. 



