PSEUDOMONAS JERUGINOSA. 307 



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 

 coagulation of the casein. 



On blood-serum and egg-albumin its growth is ac- 

 companied by liquefaction. The growth on coagulated 

 egg-albumin 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 dis- 

 coloration. 



In peptone solution (double strength) it causes a 

 bluish-green color. In one of four cultures from differ- 

 ent sources we observed the production of a distinct 

 blue color. 



It produces indol. 



It stains with the ordinary dyes, and its flagella may 

 readily be demonstated by appropriate methods of stain- 

 ing. 



It is an active producer of a proteolytic enzyme that 

 may readily be separated and its digestive properties 

 observed by the following simple method : Prepare a 

 bouillon culture of about 70 to 80 c.c. volume, and 

 allow it to grow at 37 to 38 C. for four or five days. 

 Filter through a Berkfeld filter into a sterile receiver. 

 Under aseptic precautions decant the filtrate into sterile 

 test-tubes, about 7 c.c. to each tube. Then under aseptic 

 precautions make the following tests : To one tube add a 

 small bit of hard-boiled egg (about one-half the size of 



