Preface 



Luminescence — the emission of "cold light" in the form of bioliimi- 

 nescence, chemiluminescence, fluorescence, phosphorescence, et 

 cetera — has long been a fascinating subject of inqpiry. Modern chem- 

 ical and physical research has greatly advanced the understanding of 

 fluorescence and phosphorescence, particularly of inorganic and of 

 many organic substances; within the past generation, practical appli- 

 cations have become a part of everyday experience, as witnessed by 

 such familiar examples as fluorescent lighting, phosphorescent paints 

 or tapes, and television screens. Luminescence in relation to biological 

 processes is a more difficult and complicated problem, the progress of 

 research has been seemingly slow, and the importance of studies on 

 this aspect has been less obvious. Thus, it has not yet proved possible 

 to obtain luminescent extracts from more than about half a dozen of 

 the myriads of visibly luminescent organisms that are scattered over 

 the phylogenetic tree of animals from protozoa to fishes, as well as 

 over the primitive plant world of bacteria and fungi. Furthermore, 

 basic relationships between photosynthesis, fluorescence, and chemi- 

 luminescence of chlorophyll in green plants remain to be clarified, and 

 the full significance of the property of fluorescence in many biological 

 molecules such as riboflavin is yet to be understood. 



Within the past several years, however, remarkable progress has 

 been achieved, and broad implications of luminescence in fundamental 

 biological research have become convincingly evident. The way has 

 been paved by an increasing number of investigators, as well as by 

 the ever expanding knowledge in various fields and the introduction 

 of new methods of analysis and measurements. Among our contem- 

 poraries, E. Newton Harvey is outstanding for his own extensive and 

 penetrating studies, over a period of more than four decades, as well 

 as for the work he has inspired in his students and colleagues. 



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