292 INTRACELLULAR LUMINESCENCE 



in the absence of aldehyde. With the addition of minimal concentra- 

 tions to cause a fairly bright luminescence, the kinetics of the chang- 

 ing intensity due to pressure is again different. It is difficult at the 

 moment, to arrive at an explicit hypothesis that provides a uniquely 

 probable explanation of these observations. 



The correspondence between the pressure-temperature-inhibitor 

 relationships of luminescence in living cells and in the saturated 

 extracted system argues for the fundamental similarity of the lumines- 

 cent process in cells and in these extracts. Moreover, this correspond- 

 ence shows that the earlier observations, made with intact cells and 

 interpreted in terms of simple systems, can actually be attributed to 

 the operation of relatively simple systems, rather than to extremely 

 complicated relationships existing in the highly organized chemical 

 environment of living cells, and resembling simple reactions only by 

 chance. Thus, justification is provided for the conclusions reached 

 earlier in regard to intracellular luminescence, and at the same time, 

 for further studies with the living cells, which in a number of respects 

 are more convenient to use than extracts. It is only with extracts, of 

 course, that the biochemistry of the system can be firmly established, 

 and that detailed analysis of the physical chemistiy of the system 

 can be made under fully controllable conditions. A great deal can be 

 learned also, however, from studies of the relatively simple process 

 within the immensely complex setting of a living cell. The study of 

 luminescence, in vivo as well as in vitro, is of general as well as of 

 particular interest. 



ACKNOWLEDGMENTS 



The author is indebted to Professor W. J. Kauzmann for the derivation 

 of the equation on page 290, and for critical discussions of the kinetics 

 of luminescence in bacterial extracts. The views expressed in this paper 

 are those of the author, and they do not necessarily coincide with those of 

 all the authors and co-authors of the papers referred to in this paper. 



