The Chemistry of Light-Production in Luminous Organisms. 209 



11. The production of light by the granules appears similar to the 

 cytolysis of cells, as it occurs with water (but not isotonic cane-sugar) 

 and certain cytolytic substances (saponin, chloroform, benzol, oleic 

 acid). 



12. The light-producing substances are salted out along with the 

 proteins, but are not stabile enough for chemical manipulation. 



13. The light-producing granules can not be anesthetized. 



14. Potassium cyanide has no effect on light-production. 



STUDIES ON LUMINOUS BACTERIA. 

 DESICCATION AND EXTRACTION WITH FAT SOLVENTS. 



Luminous animals may be divided into two classes — those in which 

 the luminous material is burnt within the living cell (firefly, fungi) and 

 those in which it is secreted by the cell outside (many worms, Crus- 

 tacea, and myriapods). As first shown by Mohsh (s) the luminous 

 substance must be burnt within the bacterial cell, since a dense emul- 

 sion of the luminous bacteria may be separated from the medium by 

 a Chamberland or Berkefeld filter and a clear dark filtrate with no 

 trace of phosphorescence obtained. I have repeated Mohsh's experi- 

 ment and can confirm him. An alundum filter crucible was used. 

 Can this photogenic substance in the cell be freed of other cell material 

 and obtained in a more or less pure state? We know that the bacteria 

 can be dried, and when moistened again will phosphoresce, even though 

 the majority are not living, and will give rise to no new growth if inocu- 

 lated in a suitable culture medium.^ 



These dried bacteria form the material used for extraction purposes. 

 The organisms are best grown in bulk in a thin layer of peptone (1 per 

 cent), glycerine (1 per cent), sea-water nutrient fluid covering the 

 bottom of a white enameled pie-plate and covered by another pie- 

 plate, the whole readily sterilized and serving as a large Petrie dish. 

 The medium must be faintly alkaline to phenolphthalein. The bac- 

 teria are easily collected by centrifuging. The dense mass of centri- 

 fuged bacteria is then spread in a thin layer on filter paper or on glass 

 wool, placed in a desiccator, and dried over CaCl2 in a vacuum. 

 Spreading on glass wool has the advantage that the glass wool may 

 be ground up in a mortar and a powder obtained which phosphoresces 

 when moistened, but the powder does not give so brilliant a light as 

 does the filter paper containing dried bacteria. It is well to wash the 

 glass wool with several changes of water to remove alkali. Such strips 

 of dried bacteria-impregnated filter paper can be extracted with boiling 



'I have on two occasions obtained no luminous growths from bacteria which had been dried on 

 filter paper and afterwards moistened (light was produced) with sterile sea-water and placed on 

 nutrient agar culture medium. In the majority of cases, however, colonies of brilliantly luminous 

 bacteria result. These colonies are relatively few in number, indicating that most of the bacteria 

 are killed by drj'ing. 



