FRANK H. JOHNSON 267 



that a suspension of brightly kiminescent cells could be momentarily 

 exposed to a temperature high enough practically to extinguish the 

 light, followed by a more or less complete recovery of luminescence 

 on cooling. Much later, this phenomenon was independently redis- 

 covered (Johnson, Brown, and Marsland, 1942) and provided a key 

 to the interpretation of certain temperature-pressure relationships of 

 luminescence as discussed presently. 



Quantitative studies on the intensity of luminescence during growth 



1 1 1 1 1 1 T 



I 2 3 4 9 6 T 



TIME IN HOURS 



50 



LUM. INT. > • 



CELL COUNT • O 35 * C 



k 30 



•20 ^ 



• ^ 



o 



.10 X 



is 



-I z 



ui 5 



- e 



J. 



Fig. 2. Rate of increase in cell numbers and in luminescence intensity during 

 aerobic growth of a species of luminous bacteria ( same as Fig. 1 ) in nutrient 

 broth at 35° C. (After Baylor, 1949.) 



of a luminescent species at different temperatures have shown that 

 the rate of development of luminescence may differ markedly from 

 the rate of production of cells (Figs. 1 and 2; Baylor, 1949). With 

 other things the same, the temperature coefficient for the overall 

 process of growth and cell division is evidently different from the 

 temperature coefficient for the overall process of the production and 

 functioning of the luminescent system. As a result, the intrinsic bright- 

 ness per cell may vary many-fold within a growth period of only a 

 few hours. 



