GENUS STREPTOCOCCUS 199 



in its environment. The most favorable temperature for its 

 multiplication is from 30 to 37 C. but it grows somewhat 

 slowly and feebly at the room temperature. Most pathogenic 

 streptococci give rise to hemolytic substances. This is readily 

 determined by the method given by Park. "If 1 cc. of fresh 

 or defibrinated blood is added to 6 cc. of melted agar at 40 to 

 45 C., well shaken, inoculated with characteristic streptococci 

 and poured in a Petri dish there will appear in twelve to 

 twenty-four hours tiny colonies surrounded by clear zones of 

 about 5 to 8 mm. in diameter." It possesses little pigment 

 producing power. On albuminous media it is reported to pro- 

 duce toxins soluble in water and precipitated by alcohol. 



Resistance. This is not very great. When dried in blood 

 or pus, however, some individuals may live for several months 

 at room temperature and longer in an ice- chest. In gelatin and 

 agar cultures they live for from one week to three months. In 

 order to keep streptococci alive and virulent, it is best to 

 transplant them frequently and to keep them in serum or 

 ascitic fluid bouillon in small, sealed glass tubes in the ice- 

 chest. This streptococcus is destroyed at 54 C. in ten minutes. 

 It is killed by weak solutions of corrosive sublimate (1-2500), 

 carbolic acid (1-300) and creolin (1-130) in a few minutes. 



Pathogenesis. This streptococcus is often found in pus 

 from abscesses and exudates following wound infection. It 

 is fatal for white mice and often rabbits succumb to it. It 

 tends to lose its virulence by continuous cultivation. 



A large number of streptococci have been studied from 

 different lesions, such as erysipelas, acute abscesses, septicemia, 

 cellulitis, etc. These have been described under different 

 names, but the conclusion seems to be warranted that the 

 slight differences existing between them are acquired and non- 

 permanent variations of organisms derived from the same 

 species. Certain differences have been found in S. pyogenes 

 isolated from man and from cattle. It is generally considered 

 that the streptococci associated with acute inflammatory 

 processes should be grouped under S. pyogenes. Moore * de- 

 1 Moore. Am. Vet. Review, Vol. XXIII (1900) p. 687. 



