SUPPURA TION. 163 



developing all along the line of inoculation. The green 

 pigment (fluorescin) is soluble, and soon saturates the cul- 

 ture-medium and makes it very characteristic. As the 

 culture ages, or if the medium upon which it grows 

 contains much peptone, a second pigment (pyocyanin) is 

 developed, and the bright green fades to a deep blue- 

 green, dark-blue, or in some few cases to a deep reddish- 

 brown. 



Upon potato a luxuriant greenish, smeary layer is 

 produced. 



This bacillus is highly pathogenic for laboratory ani- 

 mals. About i c.cm. of a fresh bouillon culture, if in- 

 jected into the subcutaneous tissue of a guinea-pig or a 

 rabbit, causes a rapid edema, a suppurative inflammation, 

 and death in a short time. The bacilli can be found in 

 the blood and in most of the tissues. 



Intraperitoneal injections cause suppurative peritonitis. 



It is interesting to observe, in passing, that this path- 

 ogeny can be set aside by the immunity which develops 



FIG. 52. Bacillus pyogenes foetidus, from agar-agar; x 1000 (Itzerott and 



Niemann). 



after a few inoculations with sterilized cultures. These 

 are easily prepared, as the thermal death-point deter- 

 mined by Sternberg is 56 C. 



