THE GENUS PHOTOBACTERIUM. 161 



Whereas Pfl tiger's studies were concerned with the carcases of 

 phosphorescent salt-water fish, the first microscopical examination 

 of the phosphorescent flesh of cattle slaughtered for food was 

 made by Niiesch, who also found a fission fungus, which he named 

 Bacterium lucens, to be the cause. Ludwig, in 1882, showed that 

 a transference of the mucus of phosphorescent sea-fish on to sound 

 animal flesh rendered the latter phosphorescent in turn. Unaware 

 at the time that the organism had already received two names, he 

 bestowed on it the title of Micrococcus P finger i. This was the 

 first phosphorescent bacteria obtained (in 1885) as an undoubtedly 

 pure culture. Three years later B. FISCHER (II.) proved the 

 existence of other species, three of which he himself described, 

 one of them (from the West Indian seas) being named Bacillus 

 phosphorescens, and the other two (found on German shores) he 

 called respectively Bacterium phosphorescent and "native phos- 

 phorescent bacillus." 



In 1890 BEYERINCK (XI.) proposed the generic name of Photo- 

 bacterium for the entire group of phosphorescent bacteria, and 

 more closely investigated the six undermentioned species : 



1. Photobacterium Pflilgeri. 



2. Ph. phosphorescens. 



3. Ph. balticum = Fischer's "native phosphorescent bacillus." 



4. Ph. Fischeri = Bact. phospkorescens t F. 



5. Ph. indicum = Bacillus phosphorescens, F. 



6. Ph. luminosum. 



With these six (motile) species Katz in his above-mentioned 

 treatise associated a second half-dozen species collected on the coast 

 of Australia, and EIJKMANN (I.) added a thirteenth (Photobacterium 

 javanense), repeatedly found by him on phosphorescent sea-fish in 

 the market at Batavia. 



100. The Food Requirements of Phosphorescent 

 Bacteria 



formed the subject of comprehensive investigations by Beyerinck, 

 a few of whose multifarious results obtained therefrom may be 

 given here. 



A remarkable difference exists between the first four and the 

 last two of the six species named in the foregoing list. The 

 former require at least two organic nutrient materials, the one 

 (supplying nitrogen) being a substance resembling peptone, and 

 the second a compound supplying the carbon : peptones alone, or 

 amides and the like, by themselves producing neither growth nor 

 phosphorescence. Ph. indicum and Ph. luminosum behave differ- 

 ently, peptone (or any other albuminoid substance) being of itself 

 sufficient as an organic food-stuff therefor. 



A slight addition of sugar to the medium increases the 



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