STREPTOCOCCUS PYOGENES. 137 



Agar Stab. — Stab : Thread-like, later sometimes gran- 

 ular (1, III). Surface growth: Very delicate growth, 

 transparent, gray, irregular, unimportant. Atj'pically, 

 the growth may be much more vigorous, with whitish- 

 gray color and smooth wavy border (1, iv). Similar also 

 on glycerin agar. 



Agar Streak. — As on gelatin. Water of condensation : 

 Clear with slight whitish deposit. 



Bouillon Culture. — Varies greatly in the different 

 forms, from diffuse cloudiness to the formation of a com- 

 pact sediment with clear fluid (see p. 141). 



Milk Culture. — Usually firmly coagulated in from four 

 to twenty-four hours. 



Potato Culture. — Invisible growth, at times entirely 

 absent, rarely more luxuriant (compare p. 141). 



Non-albuminous Medium. — Faint growth. 



Vitality. — In cultures usually only a few weeks. Ac- 

 cording to Petruschky, cultures on gelatin, grown for 

 forty-eight hours at 22°, if kept in an ice-box retain their 

 vitality and virulence for months. The Strept. pyogenes 

 belongs among the varieties that die quickly. Bouillon 

 cultures, if oxygen is admitted, usually live only for weeks, 

 but in hydrogen for months. 



Resistance to Drying. — Vitality and virulence are 

 retained several months, especially in dried pus. 



Chemical Activities. — (a) Chromogenesis : Almost 

 always without pigment production ; cultures were grown 

 by Kruse and Pasquale in Italy with yellowish-brown to 

 blood-red pigment. These were highly virulent, short- 

 chained forms obtained from cases of tuberculosis. 



(6) No indol, little sulphuretted hydrogen. 



(c) Acid production from carbohydrates in our cultures 

 was minimal ; no gas formation. 



According to Sieber-Schoumoff, certain cultures (Strept. erysipelatos 

 and Strept. scarlatinas) produce levorotatory lactic acid, others (Strept. 

 pyogenes) inactive lactic acid from grape- and milk-sugar. All cul- 

 tures produce, besides, some volatile fatty acids, poisonous albumoses, 

 and of gases only carbonic acid, with the exception of the form found 

 in scarlatina, which also produces hydrogen. 



Emmerling's investigations (C. B. L. IV, 342) regarding the decom- 

 position of fibrin by streptococci under anaerobic conditions gave the 

 remarkable result that a solution of fibrin was effected. He found 



