INSTANCES AND CAUSES OF LUMINOSITY 387 



Bacteria l but also to the facultatively anaerobic Bacterium phosphorescent, Beyerinck, 

 which is able to develop but not to luminesce in the absence of oxygen. It is, 

 however, quite possible that facultative anaerobes may exist which are capable of 

 emitting light in the absence of oxygen. 



The luminescence is decreased or suppressed when the partial pressure of the 

 oxygen is much increased or diminished, but no definite numerical results have been 

 obtained. According to Lehmann 2 , however, compressed air under a pressure of 

 six atmospheres, or pure oxygen under a pressure of an atmosphere, exerts no 

 perceptible effect upon the luminescence of meat or wood, whereas Fabre 3 finds 

 that the emission of light by Agaricus olearius increases in pure oxygen. The fact 

 that the luminescence of certain Bacteria only gradually disappears in the absence of 

 oxygen does not afford satisfactory evidence that these organisms store up occluded 

 oxygen. 



The emission of light is not the result of intense respiration, for the 

 latter continually increases up to the maximal temperature, whereas the 

 former rapidly ceases above a rather lower optimum temperature. In 

 addition the luminous Fungi and Bacteria do not respire with especial 

 activity 4 , while the spadix of an Aroid evolves no light during its most 

 active period of respiration and heat-production. Luminous organisms may 

 indeed evolve light when their production of heat is so slight that their 

 temperature is below that of the surrounding medium. 



Certain substances evolve light during slow oxidation without any 

 perceptible production of heat 5 , and hence it is possible that during either 

 the metabolism, or more especially the respiratory katabolism of luminous 

 organisms, materials may be produced whose slow oxidation gives rise to 

 light. According to Dubois 6 , two substances, Inciferin and luciferase, may 

 be isolated from Pholas dactylus. These evolve light when brought into 

 contact and therefore presumably are responsible for the emission of light by 



1 Pfliiger, I.e., p. 223; B. Fischer, I.e., 1887, p. 37; Lehmann, I.e., 1889, p. 788; Beyerinck, 

 I.e., 1889; Katz, I.e., 1891, p. 314; Eijkmann, I.e., 1892, p. 657. 



2 K. B. Lehmann, Einfluss des comprimirten Sauerstoffs auf d. Lebensprocesse, Zurich, 1883, 

 p. 87. [Dessaignes (1. c., p. 29) also observed no increased luminosity of wood in pure oxygen, 

 whereas Nees, Noggerath, and Bischoff (1. c., p. 693) state that it increased ; and Heinrich (1. c., 

 p. 332) found that it increased in air at a pressure of two atmospheres, but not in pure oxygen. 

 These varying results are probably due to the influence of fatigue and of accommodation upon the 

 visual judgement of the intensity of a feeble source of illumination, a striking instance of which is 

 afforded by the statements of different observers in regard to Blondhlot's ' n rays.'] 



3 Fabre, I.e., p. 191. 



4 Fabre (I.e., p. 193) found that Agarictts olearius respired most actively during the luminous 

 condition. 



5 Radziszewski (Ann. d. Chemie, 1880, Bd. ccin, p. 330; Ber. d. chem. Ges., 1877, p. 321; 

 1883, p. 597) states that lophin dissolved in alkali, and liver oil dissolved in toluol containing a few 

 drops of cholin or nenrin solution, emits light at as low a temperature as ioC. Dubois (Compt. 

 rend., 1901, T. cxxxil, p. 431) has shown that aesculin dissolved in alcoholic potash phosphoresces. 



6 Dubois, Le9ons de Physiologic, 1898, p. 524 ; Compt. rend., 1896, T. cxxill, p. 653. Dubois 

 formerly had expressed the opinion that the emission of light was produced by the conversion of 

 colloids into crystalloids. 



C C 2 



