368 APPLICATION OF METHODS OF BACTERIOLOGY 



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? 



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 position; let 

 that in the other remain fluid. On the surface of the former 

 pour 0.5 c.c. of the pyocyaneus filtrate, and mark the point 

 of contact between the gelatin and filtrate. To the other 

 tube add a similar amount of filtrate, mix thoroughly, and 

 solidify in a glass of cold water. 



At the end of eighteen to twenty hours note result. Is 

 it possible to solidify again the gelatin through which the 

 filtrate was mixed, by placing the tube in cold water? 



Do the activities of this enzyme suggest those of any of 



