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193                 PATHOGENIC BACTERIA.

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

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 injected
into the ear vein was fatal to a rabbit.

Petruschky2 found the virulence of the culture to be
well retained if the culture was planted in gelatin, trans-
planted every five days, and when grown kept on ice.

Hoist3 succeeded in keeping an exceedingly virulent
Streptococcus brevis on artificial culture-media for eight

1  Ann. de VInst. Pastettr, Tome ix., No. 7, July 25, 1895, p. 593-

2  Centralbl. fur Bakt. und Parasitenk., Bd. xviii., No. 16, May 4, 1895, p,
551-                                       3 Ibid., Bd. xtx., No. n, Mar. 21, 1896.