244 



LIGHT AND LIFE 



ex = 365 rn^ 



Fig. 23. Relative fluorescence spectra of lucifcrin. The measurements were made 

 at various temperatures, beginning at — 195°C for curve 1 and increasing to room 

 temperature for curve 8. The large apparent peak around 4()() ni^u is due to the 

 scatter of the exciting light by the crystalline ice at the low temperatures. 



Qiiantiun Yield oj Firefly Biohiminescence 



In considering the mechanism of the firefly light-emitting system 

 it was essential that \vc have some understanding of the number of 

 light quanta emitted per luciferin molecule used. 



The absolute spectral sensitivity of a phototube was determined 

 using an NHS standard of radiation intensity and a sensitive thermo- 

 pile in combination with a quart/, prism monochromator. With this 

 phototube it was possible to determine quantitatively the total num- 



