256 PATHOGENIC BACTERIA. 



The organism seems to grow well in milk, which is 

 coagulated and digested. 



The streptococcus is not very sensitive to acids, and 

 can be grown quite well in media with a slightly acid 

 reaction. 



Sternberg found that the streptococci succumb to a 

 temperature of 52°-54° C. continued for ten minutes. 



Their vitality in culture is not great. Unless fre- 

 quently transplanted they die. In bouillon they are said 

 to die in five to ten days. On solid media they seem 

 to retain their vegetative and pathogenic powers much 

 longer. They resist drying well. Their growth in arti- 

 ficial media is accompanied by the production of an 

 acid which probably acts destructively upon the bacteria 

 themselves. 



The Streptococcus pyogenes is generally not very patho- 

 genic for animals. Subcutaneous injections into mice 

 and rabbits are, as a rule, without either general or local 

 manifestations of importance. If, however, an ear of a 

 rabbit is carefully inoculated with a small amount of a 

 pure culture, a small patch resembling erysipelas usually 

 results. The disturbance passes away in a few days and 

 the animal recovers. 



If, however, the streptococcus is highly virulent, the 

 rabbit dies in from twenty-four hours to six days from 

 a general septicemia. The cocci may be found in large 

 numbers in the heart's blood and in the organs. In less 

 virulent cases minute disseminated abscesses are some- 

 times found. 



According to Marmorek, 1 the virulence can be increased 

 to a remarkable degree by rapid passage through rabbits, 

 and maintained by the use of a culture-medium consist- 

 ing of three parts of human blood-serum and one of 

 bouillon. The blood of the ass, and ascitic and chest 

 fluids may also be used. By these means Marmorek suc- 

 ceeded in intensifying the virulence of his culture to such 

 a degree that one hundred millionth of a c.cm. injected 

 into the ear vein was fatal to a rabbit. 



1 Ann. de P Inst. Pasteur, Tome ix., No. 7, July 25, 1895, p. 593. 



