PSP1VDOMONAS ^ERUGINOSA. 313 



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 demonstrated by Loffler's method of staining. 



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 

 a pea) and place in an incubator. Render another tube 

 slightly acid with dilute hydrochloric acid, and add a 

 bit of the white of egg to it also. Do the results differ? 



Heat another tube to 80 C. for fifteen minutes, and 

 repeat the experiment. Has the heating had any effect? 



To another tube add carbolic acid to the extent of 2 

 or 3 per cent. Is the digestive activity of the solution 

 modified ? 



To two ordinary tubes of gelatin add carbolic acid 

 until it is present to the extent of 0.25 per cent, in each 

 tube. Solidify the gelatin in one tube in the upright 



