THE CHEMISTRY OF BACTERIA. 117 



kept in a dark place, will not infrequently phosphoresce. 

 When such fish are kept in meat-shops, it may happen that 

 veal, pork and beef will, likewise, develop this strange 

 property. This phenomenon is met with especially in sea- 

 coast towns. The river and lake waters do not phosphor- 

 esce, nor do the fish taken from such waters. Instances of 

 phosphorescence are met with inland, in the well-known 

 fox- or punk-fire which is observed in the woods at night, 

 on the surface of old stumps. The fire-fly or glow-worm 

 affords another illustration. 



Phosphorescence, like pigment production, or fermen 

 tation, is a vital phenomenon. It has been known for a 

 long time that certain protozoa in the sea-water emit light. 

 Moreover, this property has been observed in some algae 

 and the ordinary fox-fire is due, unquestionably, to certain 

 moulds. It is only within comparatively recent times that 

 bacteria have been shown to possess this strange power. 

 Pfluger's observation, in 1874, rendered it probable that cer- 

 tain bacteria were the cause of the phosphorescence ob- 

 served on fish and meat, but it was not until 1887, when 

 Fischer obtained pure cultures, that the cause was de- 

 monstrated. The mysterious glow on fish and meats like 

 the pigmented milk, meat or starchy food is, therefore, due 

 to the presence and growth of bacteria. In both cases, the 

 microscope has revealed the cause which in the past was 

 but too often ascribed to sorcery, or to supernatural powers. 



At the present time about 25 species of phosphorescing 

 bacteria are known. It is quite likely that some of these 

 may be mere varieties. They are without exception inhab- 

 itants of salt-water. In large rivers, such as the Elbe, 

 phosphorescing vibrios have been found which, otherwise, 

 resemble the vibrio of Asiatic cholera. It is possible that 

 these vibrios are derived from the sea. All the phosphor- 

 escing bacteria known are aerobic and, with possibly one 

 exception, are non-pathogenic. . They are, with the excep- 

 tion of one micrococcus and the vibrios mentioned, all rod- 



