THE CHEMISTRY OF LIGHT PRODUCTION 99 



obtained by electrometric measurements of H-ion con- 

 centration, that no carbon dioxide is produced during 

 luminescence of luminous animals. 



In most animal cells it is perfectly clear that lumines- 

 cence does not accompany respiration, since respiration 

 is a continuous process, whereas light is only produced 

 on stimulation. It is true that on stimulation respiration 

 is accelerated, and we might suppose that luminescence is 

 an accompaniment of accelerated respiratory oxidations ; 

 but this is not the case, for in luminous animals a rise in 

 temperature of ten degrees centigrade will accelerate 

 the respiratory oxidations 250 per cent, without neces- 

 sarily causing the production of light. 



In fungi and bacteria, on the other hand, which con- 

 tinually emit light, it is quite natural to suppose that the 

 light is an accompaniment of respiration, just as we 

 know the heat of these forms to be. This view was accepted 

 by such of the earlier workers as Fabre in 1855, who 

 found that luminous portions of a mushroom, Agaricus 

 olearius, gave off more CO2 (4.41 c.c. CO2 per gram in 

 36 hours at 12"^ C.) than non-luminous portions (2.88 c.c. 

 CO2 per gram in 36 hours at 12 ° C. ) . This experiment has 

 never been repeated and there are many reasons besides 

 luminescence why one piece of fungus might have a more 

 rapid respiratory rate than another piece. It is not true 

 that rapidly respiring plant tissues, such as germinating 

 seeds or the spadix of AracecB, are luminous, although 

 they produce considerable heat. 



On the other hand, it is very easy to prove that lumi- 

 nescence, even in bacteria, is not connected with respira- 

 tion. Thus, Beijerinck (1889 c) found that of several 

 species of luminous bacteria studied by him, one, Bac- 



