214 McKenney — On Luminovs Hacteria. 



Literature. 



It is only a quarter of a century since Pfliiger discovered the first 

 luminous bacterium — Micrococcus 2)7ios2)Jit)rens, Cohn.* Previous to 

 this discovery, Pfliiger had expressed the belief that the (so-called) phos- 

 phorescence phenomena would prove to be intimately connected with 

 the respiratory processes. He obtained confirmation of this belief when 

 by experiment he showed the need of free oxygen for the production of 

 light by the newly discovered bacterium. Since light production then 

 seemed bound up with respiration, Pfliiger asserted that luminescence 

 was a vital phenomenon — that it was inseparably bound up with life. 

 Those who had studied luminosity in animals before Plliiger's discover)' 

 of luminovis bacteria had arrived at the conclusion that it was the pro- 

 toplasm which was luminous — that the luminous matter was "lebendiges 

 Eiweiss." Pfliiger's experiments apparently confirmed this position. 



In 1880, Radziszewski attacked the question from the chemical stand- 

 point. It had previously been known that certain substances when 

 raised to a certain temperature could be made to emit light. Radzis- 

 zewski discovered a large number of additional non-living organic com- 

 pounds which could be made to give out light. He also found that in 

 many cases a high temperature was not required and that with lophin 

 no higher temperature than 10° was needed. Fvirther he ascertained 

 that the conditions of luminescence were a markedly alkaline reaction 

 and a slow oxidation. Organic and inorganic bases might be employed 

 to produce the alkaline reaction. The light produced by these substances 

 has a spectrum very closely resembling that of the photogenic forms — 

 giving a continuous band between D and G, with the brightest part be- 

 tween E and F. In view of the resemblance of the spectra of the light 

 produced by these chemicals and by luminousorganisms, Radziszewski is 

 of the opinion that the light of luminous organisms is due to the presence of 

 certain of the photogenic substances which he discovered. While Rad- 

 ziszewski differs from Pfiiiger in holding luminescence not to be a vital 

 phenomenon, yet both agree that oxidation plays a very important role 

 in luminescence. Dubois records a symbiotic relation between a marine 

 mollusk and a species of bacterium. In this case Dubois asserts that 

 the animal excretes a substance "Luciferin" which through action of 

 the bacterium is caused to emit light. 



Beijerinck, who has studied a number of forms, finds that light ceases 

 with the death of the bacteria and that the light intensity may be 

 diminished or increased by varying the nature of the nutrient media. 

 His conclusion concerning luminescence is, that it is a vital process — that 

 it is due to the liberation of radiant energy by the oxidation of peptone 

 at the moment of its conversion into living protoplasm. 



The observations of ]}. Fischer, Forster, Lehmann and Tolhausen of 

 the production of light at and below 0° seem hardly to agree with the 



*Since 1875 there has been as many as twenty-five species of luminous 

 bacteria recorded from widely separated parts of the world. In all 

 probability, many of these species names will prove to be synonyms, or 

 at least varieties. 



