92 THE NATURE OF ANIMAL LIGHT 



tissues cells themselves and respiration in the chemical 

 sense has come to mean this universal slow combustion 

 in the cells of the body rather than the breathing move- 

 ments of the lungs themselves. In anaerobic respiration, 

 CO2 is given off, but no oxygen absorbed. In aerobic 

 respiration, oxygen is absorbed and CO2 given off. In 

 addition we know of many substances which oxidize by tak- 

 ing up oxygen without giving off CO2. We have seen that 

 oxygen must be absorbed for luminescence of animals and 

 we may now inquire whether CO2 is given off and the rela- 

 tion between respiration and light production. 



To determine if CO2 is given off during luminescence it 

 is necessary to work with fairly pure luminous materials, 

 obtained from luminous organisms. It is impossible to 

 use the living organisms themselves as the CO2 continually 

 respired becomes a very disturbing factor. From Gypri- 

 dina, a small crustacean, two materials soluble in water 

 may be prepared {luciferin and lucif erase), which will 

 givfe a brilliant luminescence on mixiag. It is possible to 

 determine the H-ion concentration of the two solutions 

 separately and of the mixture of the two after the lumi- 

 nescence has occurred. 



If CO2 is produced during luminescence the H-ion con- 

 centration of the luminous solution should increase. Meas- 

 urements made electrometrically with the hydrogen elec- 

 trode have failed to demonstrate any increase in acidity. 

 The Ph of both solutions and of a mixture of the two is 

 9.04. This would indicate that CO2 is not produced. As 

 both luminous solutions contain proteins and the luminous 

 substances themselves are probably proteins, which have 

 a high buffer value, a method of this kind is none too sensi- 

 tive. However, we can definitely state that not enough 



