Streptococcus Pyogenes 301 



usually recover. Guinea-pigs, cats, and dogs are but 

 slightly susceptible. Large animals, like sheep, goats, cattle, 

 and horses, react very slightly to large doses, but sometimes 

 suffer from abscesses at the seat of injection. Mice die in 

 from one to four days from general infection. If the organ- 

 isms are less virulent, they die in from four to six days with 

 edema and abscess formation at the site of inoculation, and 

 subsequent invasion of the body. The streptococcus seems 

 to be most pathogenic for that species of animal from which 

 it has been isolated. 



If the ear of a rabbit be carefully inoculated with a 

 small quantity of a pure culture, local erysipelas usually 

 results, the disturbance passing away in a few days and the 

 animal recovering. If, however, the streptococcus be 

 highly virulent, the rabbit dies of general septicemia in 

 from twenty-four hours to six days. The cocci may then 

 be found in large numbers in the heart's blood and in the 

 organs. In less virulent cases minute disseminated pyemic 

 abscesses are sometimes found. 



According to Marmorek,* the virulence of the strepto- 

 coccus can be increased to a remarkable degree by rapid 

 passage through rabbits, and maintained by the use of a cul- 

 ture medium consisting of three parts of human blood-serum 

 and one of bouillon. The blood of the ass or ascitic or pleu- 

 ritic exudates may be used instead of the human blood-serum 

 if the latter be unobtainable. By these means Marmorek 

 succeeded in intensifying the virulence of a culture to such 

 a degree that one hundred-thousand-millionth (un cent mil- 

 liardibme) of a cubic centimeter injected into the ear vein 

 was fatal to a rabbit. 



Petruschky f found the virulence of the culture to be well 

 retained when the organisms were planted in gelatin, trans- 

 planted every five days, and when grown, kept on ice. 



Hoist t observed a virulent Streptococcus brevis that re- 

 mained unchanged upon artificial culture media for eight 

 years without any particular precautions having been taken 

 to maintain the virulence. 



Dried streptococci are said by Frosch and Kolle to retain 

 their virulence longer than those growing on culture media. 



* "Ann. de PInst. Pasteur," t. ix, No. 7, July 25, 1895, p. 593. 

 t"Centralbl. f. Bakt. u. Parasitenk.," Bd. xvm, No. 16, May 4, 

 i895, P- 551- 



t Ibid., Bd. xix, No. n, Ma.rch 21, 1896. 

 Fliigge's " Die Mikroorganismen." 



