THE BACILLUS PYOOYANUS. 251 



On potato the growth is brownish, dry, and slightly 

 elevated above the surface. With some cultures the 

 potato about the growth becomes green ; with others this 

 change is not so noticeable. With many cultures a 

 peculiar phenomenon may be produced by lightly touch- 

 ing the growth with a sterilized platinum needle. This 

 phenomenon consists in a change of color from brown 

 to green at the point touched. It is best seen in cultures 

 that have been 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 

 from ten minutes to half an hour. This is the " cha- 

 meleon phenomenon " of Paul Ernst. 



In bouillon the green color appears, and the growth 

 is seen in the form of delicate flocculi. A very delicate 

 mycoderma is also produced. 



In milk it causes an acid reaction, with coincident 

 coagulation of the casein. 



On blood serum and egg albumin its growth is accom- 

 panied 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 discoloration. 



In peptone solution (double strength) it causes a 

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

 ferent sources there was a blue color produced. 



It produces indol. 



It stains with the ordinary dyes, and its flagella may 

 be readily demonstrated by Lreffler's method of staining. 



Inoculation into animals. As a rule, cultures of this 

 organism obtained directly from the discharges of a 

 wound are capable, when introduced into animals, of 



