PSEUDOMONAS AERUGINOSA 367 



kept in the incubator for from seventy-two to ninety-six 

 hours. It occurs in from one to three minutes after touching 

 with the needle, and may last for from ten minutes to a half- 

 hour. This is the " chameleon phenomenon" of Paul Ernst. 



In bouillon the green color appears, and the growth is 

 seen in the form of delicate flocculi. A very delicate myco- 

 derma is also produced. As growth progresses, the bouillon 

 becomes darker and darker in color, and more or less fluores- 

 cent, until it finally is about comparable in this respect to 

 crude petroleum; at the same time it assumes a peculiar 

 ropiness, and very old cultures (four to six weeks in the incu- 

 bator) may attain about the consistency of raw egg-albumen. 

 This is due to the production of a substance closely allied, 

 chemically speaking, to mucin. Whether it is a metabolic 

 product or one resulting from the degeneration or the auto- 

 digestion, so to speak, of the bacteria, cannot now be said; 

 at all events, in cultures presenting this peculiarity very 

 few bacteria of normal appearance — indeed, very few 

 bacteria at all — are to be seen on microscopic examination. 



In milk it causes an acid reaction, with coincident coagula- 

 tion of the casein. 



On blood-serum and egg-albumen its growth is accom- 

 panied by liquefaction. The growth on coagulated egg- 

 albumen is seen as a dirty-gray deposit surrounded by a 

 narrow brownish zone; the remaining portion of the medium 

 is bright green in color. As the culture becomes older the 

 green may give way to a brown discoloration. 



In peptone solution it causes a bluish-green color. In 

 one of four cultures from different sources we observed the 

 production of a distinct blue color. In another specimen 

 the fluid was of a distinct wine red color, after 5 days at 

 body temperature. 



