STREPTOCOCCUS. 517 



which do not stain by Gram's method, those with 

 which we are concerned invariably react positively. 

 Streptococci are never motile, possess no flagellas 

 and form no spores. 



Streptococci grow better in a neutral or slightly cultivation 

 alkaline medium than in one of acid reaction, but 

 virulence is lost rapidly. They may be cultivated 

 indefinitely in media which contain serum or 

 ascitic fluid., but even here virulence disappears 

 gradually; frequent transplantation is necessary. 

 In bouillon those strains which produce short 

 chains or grow as diplococci cause a diffuse cloud- 

 ing of the medium, whereas those growing in long 

 chains sink to the bottom,, leaving a clear overly- 

 ing fluid. Streptococci demand little oxygen, all 

 are facultative anaerobes and some are said to be 

 obligate anaerobes; obligate anaerobes may be cul- 

 tivated from the vagina and intestines. The 

 optimum temperature for growth is 37 C. 



When dried, streptococci live for from ten days Resistance. 

 to several weeks; they are destroyed more quickly 

 in the presence of sunlight. Susceptibility to 

 antiseptics depends on the nature of the medium 

 in which they are suspended or imbedded. When 

 unprotected by bouillon or other fluid they are 

 killed in a few seconds by 1/1000 corrosive sub- 

 limate and 3 per cent, carbolic acid (Fehleisen) ; 

 when in bouillon, by 1/1500 corrosive sublimate 

 and by 1/200 carbolic acid in fifteen minutes. Ly- 

 ing on a mucous surface, where they are imbedded 

 in mucus or tissue fluids, they are protected 

 against antiseptics to some extent. They are fairly 

 resistant to heat, being destroyed by a temperature 

 of 70 to 75 C. in one hour (v. Lingelsheim). 



