/•. H. JOHNSON, E. H.-C. S/E, AM) ) . HANEDA 207 



then (ooliiig (juickly, (2) triturating a similar organ in a little water 

 at room tempcratiuv until the light disappeared, and (3) pouring 

 the two preparations together in the dark, whereupon light appeared 

 at once. 



Because the quantity of pliotogenic sul)stances in Pyrophorus 

 seemed to be small and the specimens were hard to procure, he 

 sought more iavorable material and loiuid it in the hniiinous clam, 

 Pliolas (idctyliis, which yielded analogous extracts that were active in 

 light emission in response to essentially the same j^rocedure (10) . 

 With Pliolas, the hot water extracts were prepared by heating to 

 70°C, rather than boiling, in order to conserve the relatively, but 

 not fully, heat-stable component. The relatively heat-labile com- 

 ponent ^\■as rapidly eliminated at 60° C. For the active principle 

 in the hot water extract he introduced the name "luciferin," and for 

 the one in the cold water extract the name "luciferase" (10) . In- 

 vestigation of the properties of these components led him to conclude 

 that the former was a natinal albumin whose oxidation by molecu- 

 lar oxygen was catalyzed by the latter, a specific enzyme, vjith. the 

 production of light. This conclusion w^as correct except for the 

 chemical nature of the luciferin, which is not an albumin. 



In terms of the above procedine, the expression "luciferin-luciferase 

 reaction" can be clearly defined, namely, light emission on mixing a 

 cooled, hot water extract, whose luminescence was destroyed by heat- 

 ing, with triturated photogenic cells or tissue, whose luminescence 

 has disappeared by other causes. In terms of the information that 

 such a procedine yields, how^ever, the expression can have as many 

 meanings as such widely encompassing terms as "protein denatura- 

 tion," For reasons that are now understandable, a negative result, 

 i.e., failure to obtain light on mixing crude extracts, does not prove 

 the absence of luciferin or luciferase or even of a reaction between 

 the two. Conversely, positive results do not prove that the observed 

 light has originated in the manner in which it seemed to, i.e., from 

 a reaction between the presumed components. Testing for a luciferin- 

 luciferase reaction in extracts of various types of organisms is never- 

 theless an important preliminary step, since the separation of com- 

 ponents that will give a luminescent reaction in vitro is a sine qua 

 nou in progress toward biochemical elucidation of the system. 



Shortly before Dubois' book appeared, the first paper in a long, 

 comprehensive series of studies on bioluminescence by the late Pro- 

 fessor E. Newton Harvey (17) was published. No few words of tribute 

 could possibly do justice to the magnitude of his work, and the 



