1899 | PRODUCTION OF FLUORESCENT PIGMENT 25 
for a series of generations in such simple media as I have used. 
In a solution of 0.2 per cent. asparagin, 0.1 per cent. sodium 
phosphate, and 0.0001 per cent. magnesium sulfate, B. #7, albus 
is able to develop a fairly intense color. If from a culture in 
this medium a second tube of the same solution is infected, and 
the procedure repeated at intervals of three days, neither 
attenuation nor exaltation of the fluorescigenic power can be 
noticed after thirteen successive transfers. The same statement 
holds true of the action of B. fl. putridus in a solution containing 
0.25 per cent. ammonium lactate, 0.1 per cent. sodium phos- 
phate, and 0.1 per cent. magnesium sulfate. 
The solutions of the ammonium salts of the organic acids, 
with the exception of the urate, contained respectively 0.5 per 
cent. of the ammonium salt and o.1 per cent. each of neutral 
sodium phosphate and magnesium sulfate. Ammonium succin- 
ate, lactate, and citrate all proved to be substances well adapted 
for the production of the fluorescent pigment. The color 
appears more speedily in the succinate and lactate, and with 
most species becomes also more intense than in the citrate. 
In the succinate solution all of the species but one developed 
pigment quickly and intensely. The color developed very 
tardily in the culture of B. #2. putridus, and never became intense. 
In ammonium /actate solution, a fine color developed within two 
days in the cultures of B. fl. albus, B. viridans, B. ft. tenuis, and 
B, ft. mesentericus; B. fl. liquefaciens was from ten to twelve hours 
behind the others at this stage, but eventually produced a very 
deep color; B. ff. putridus showed a much fainter tinge of color 
after ten days, and the color never became pronounced. 
The ammonium citrate solution did not, on the whole, lend 
itself to the production of pigment quite as readily as the lactate 
and succinate. JB. fi. albus, B. fl. tenuis, and B. fi. mesentericus, 
indeed, seemed to flourish and produce pigment nearly as well 
as in lactate or succinate, but B. viridans and B. liquefaciens 
showed a decidedly less rapid growth, while B. 7. putridus 
caused only a very slight turbidity and developed no trace of 
color. 
