PHOSPHORESCENCE OB PHOTOGENESIS 99 



PRODUCTION OF "AROMATIC" COMPOUNDS. 



These have been mentioned in discussing the putrefac- 

 tion of proteins, as indol, skatol, phenol and various cresols. 

 Of these only the first is ordinarily tested for in the study 

 of bacteria, though others of the group become of value in 

 certain special cases. 



Fig. 71. — Culture ot phosphorescent bacteria in an Ehrlenmeyor flask 

 photographed by their own light. Time of exposure twelve hours. (Molisch, 

 from Lafar.) 



PHOSPHORESCENCE OR PHOTOGENESIS. 



This is a most interesting phenomenon associated with 

 the growth of some bacteria. The "fox fire" frequently seen 

 on decaying wood which is covered with a slimy deposit is 

 most commonly due to bacteria, though also to other fungi. 

 Phosphorescent bacteria are very common in sea water, 



