C—O OOo — ll 
ee ee a a 
1899 ] PRODUCTION OF FLUORESCENT PIGMENT 27 
merest dash of color in the tube of B. viridans, and none at 
all in that of B. 77. putridus. 
Ammonium ace¢afe solution gave on the first trial a slight tur- 
bidity with B. viridans, but no sign of growth with any of the 
other species. The acetate solution was found, however, to have 
quite a decided acid reaction, and on rendering it slightly alkaline 
with ammonia, all the species except B. fi. putridus became able 
to produce a very considerable quantity of pigment. 
Ammonium oxalate solution is not adapted to the production 
of pigment although capable of supporting growth. B. 7. albus 
and B, fl. tenuis cause decided turbidity, but never develop any 
trace of fluorescent pigment even when alkali is added to the 
medium. The other species show varying degrees of cloudiness. 
If a more dilute solution be employed (0.05 per cent. oxalate), 
a faint tinge of color appears in the culture of B. ff. iquefaciens, 
and the merest suggestion of fluorescence is shown in the tubes 
of B. fi. albus, B. fl. tenuis and B. fl. mesentericus. 
In ammonium formate solution the conditions for growth and 
pigment production are still less favorable than in oxalate; in the 
ordinary solution the tubes remain perfectly clear. If the solu- 
tion be made slightly alkaline, however, a faint tinge of color 
appears in the culture of B. fi. Liquefaciens, but the other species, 
while producing a slight turbidity, never form pigment. 
INFLUENCE OF CONCENTRATION OF THE MEDIUM. 
Considerable influence upon the production of pigment is 
exerted by the degree of concentration of the medium. In 
Uschinsky’s solution,’? which consists of glycerin 30-40%, sodium 
chlorid 5~78™, calcium chlorid 0.18", magnesium sulfate 0.2— 
0.4%", di-potassium phosphate 2-2.58", ammonium lactate 6- 
7=™, sodium aspartate 3—4*™, dissolved in 1000% of water, some 
of the species, notably B. #2. albus and B. ft. mesentericus, grow 
luxuriantly and produce a goodly quantity of pigment, but the 
intensity of color never reaches as high a point as in some of 
the simpler solutions, and the color assumes much earlier the 
7 Centralbl. f. Bakt. 14:316. 1893. 
