PATHOGENIC BACTERIA. 245 



The Streptococcus pyogenes is not motile. It stains by 

 Gram's method. By the method of Hiss (page 46) capsules may 

 sometimes be demonstrated. It is facultatively anaerobic; 

 grows best in the incubator; more slowly at room tempera- 

 ture, and does not hquefy gelatin. In gelatin plates it produces 

 small, round, white, punctiform colonies which are slow of 

 development, and are visible only after about three days. It 

 grows on the ordinary media, but according to some authors 



• 



/ - 



-% 



c 



I 



^»«»«M< 



Fig. 62. — Streptococcus Pyogenes, prom a Pure Culture. (X 1000.) 



it does not grow on potato. Milk may or may not be coagu- 

 lated. The growths are never very luxuriant, and may die out 

 after a few transplantations. 



It is killed by exposure to 52° to 54° C. in ten minutes. 

 The Streptococcus pyogenes occurs frequently on the mucous 

 surfaces of the healthy body. It is often found in pus, espe- 

 cially pus of spreading inflammations of the kind known as 

 cellulitis. This organism is the commonest infectious agent 

 in puerperal fever, metritis and peritonitis. It occurs com- 



