388 APPLICATION OF METHODS OF BACTERIOLOGY 



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 five days at 

 body temperature. 



It produces indol. 



It stains with the ordinary dyes, and its flagella may 

 readily be demonstrated by appropriate methods 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 Berkefeld 

 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 incu- 

 bator. 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? 



