WILLIAM R. AMBERSON 519 



5 minutes until the extracted particles have settled out well. The 

 clear supernatant solution is then carefully decanted and used as 

 needed, I have not attempted to filter such solutions, since I early- 

 found that the time used, and exposure to air required, brought 

 about a great diminution in luciferin concentration, due to the spon- 

 taneous oxidation already mentioned. This spontaneous reaction 

 has entered in at various points to complicate the problem. It will 

 later be considered in more detail. 



The Photographic Method. 



Many students of the physics of light have interested themselves 

 in the kinetics of the true inorganic phosphorescences. For a dis- 

 cussion of this field and references to its extensive literature the 

 reader is referred to the memoir of Nichols and Merritt.^ Direct 

 photometric methods have been universally employed in such work. 

 No previous studies of a similar sort on the time relations of either 

 chemiluminescent or bioluminescent reactions have been reported. 

 In the present work I have attempted to photograph the reaction, 

 by developing a method of photographic photometry. 



At first glance it might appear that in such a problem a direct 

 photometric study is feasible and advisable. I was early convinced 

 by a number of considerations that this was not the case in an animal 

 light reaction. The rapidity of the decay in such aqueous solutions 

 as seemed best for study, together with the low intensities of light 

 involved, would make it very difficult, if not impossible, to follow 

 the reaction in this way. The final, and absolutely determining 

 consideration, was that for such studies as those involving the efi'ect 

 of concentration of enzyme and substrate, which I wished to attempt, 

 it would be necessary to investigate two solutions simultaneously. 

 This simultaneous study is necessitated by the fact of rapid deteri- 

 oration in luciferin solutions, already referred to, so that successive 

 studies of two originally identical portions of such a solution could 

 not possibly give comparable results. A photographic method 

 presented the only possibihty for such simultaneous studies. 



* Nichols, E. L. and Merritt, E., Studies in luminescence, Carnegie Inst. Wash- 

 ington, Pub. No. 152, 1912. 



