PSEUDOMONAS ^BUGINOSA 365 



organism and allow it to stand, without shaking, in the 

 incubator at body temperature for about a week. Note 

 its condition on removal. Now agitate it thoroughly with 

 air; best by pouring it into a beaker and stirring with a 

 glass rod. Note what now occurs. Now abstract with 5 c.c. 

 of chloroform — again the blue extract of "pyoscyanin" 

 is obtained. The dirty yellowish or reddish-yellow color 

 of the supernatant fluid, somewhat fluorescent, is due to 

 a yellowish pigment, soluable in alcohol and water, known 

 as "fluorescin." 



Cultivate the organism in one or another of the synthe- 

 sized media — Frankel's modification of Uschinsky's medium, 

 for instance : 



Does it produce any color? Is chloroform extract of such 

 cultures colored? How do you explain the result? 



Obtain from the water or the soil an organism that in 

 several particulars suggests B. pyocyaneus, namely, bac- 

 illus fluorescens liqiiefaciens. Repeat the foregoing cul- 

 tivations and tests. In what way do the results differ from 

 those obtained with B. pyoscyaneus? 



Make two bouillon cultures of bacillus fluorescens lique- 

 faciens. Place one in the incubator and keep the other at 

 room-temperature. How do they differ at end of 48 hours? 



Its growth in gelatin-stab-cultures is accompanied by 

 liquefaction and the diffusion of a bright-green color 

 throughout the surrounding unliquefied medium. As 



