E. NEWTON HARVEY 5 



occurs, either as a result of secretory nerve stimulation in forms with 

 extracellular luminescence, or from an effect similar to the action of 

 a motor nerve on a muscle, from the impulse of what might be called 

 a "luminor nerve," rather than a "luminous nerve." The recording of 

 light from stimulation of nerves or luminous tissue is a field of special 

 interest, first studied with luminous beetles (Snell, 1931, 1932; Brown 

 and King, 1931; Harvey, 1931), and recently greatly extended by 

 Nicol (1952, 1953), and by Harvey and Chang (1954). The results 

 will be considered in detail in this volume. 



Another field of considerable interest which should be investigated 

 with modern equipment and microelectrode technique is the electrical 

 change accompanying luminescence. A beginning has been made by 

 Hasama ( 1939-1944 ) , who has published "electroluminograms" repre- 

 senting the electrical potential change during luminescence of the 

 glowworm, the firefly, the worm Chaetopteriis, the mollusc Plocamo- 

 phorus, and the pennatulid Cavernularia. 



No physiological or biochemical investigation can be considered 

 adequate without a knowledge of the histology, particularly the fine 

 structure of luminous cells or tissue. The extent to which this is 

 known among various luminous groups and the regions for further 

 research are indicated in Table I, column 3. That the light generally 

 arises from cellular granules is a most significant and important 

 observation deserving further study. 



Bacterial and fungal luminescence, in which steady state conditions 

 determine the amount of photogenic material undergoing change, are 

 probably the most difficult to analyze from the chemical standpoint. 

 Precursors of the photogen, as well as reaction products and various 

 enzyme systems, may be expected to influence the continuous lumines- 

 cence. A continuation of the kinetic studies on bacterial luminescence 

 initiated by Johnson and collaborators (see 1954) is much to be de- 

 sired. It is also to be expected that extracellular luminescent systems 

 should be different from intracellular ones as in bacteria or those of 

 the firefly. In the firefly, the cell reactions are designed for building up 

 a supply of photogen which suddenly reacts with a flash of light fol- 

 lowing stimulation. Like bacteria, the firefly luminous cells must con- 

 tain the precursors of the photogen and also the reaction products, 

 as well as various enzyme systems. 



