SUPPURATION.	191
Upon gelatin plates very small colonies of translucent
appearance are observed. When superficial, they spread
out to form flat disks about 0.5 mm. in diameter. The
microscope shows them to be irregular and granular, to
have a slightly yellowish color, and to have numerous
irregularities around the edges, due to projecting chains
of the cocci. No liquefaction occurs.
In gelatin puncture-cultures no liquefaction is observed.
The minute spherical colonies grow along the whole
needle-track and form a slightly opaque granular line.
Upon agar-agar an exceedingly delicate transparent
growth develops slowly along the line of inoculation.
It consists of almost transparent, colorless small colonies
which do not become confluent.
The growth upon blood-serum much resembles that
upon agar-agar. . The streptococcus does not seem to
grow upon potato.
In bouillon the cocci develop rather slowly, seeming
to prefer .a neutral or feebly acid reaction. The culture-
medium remains clear, while numerous small flocculi are
suspended in it. . When the flocculi-formation is very
distinct the name Streptococcus conglomerates is used
to describe the organism. These masses sometimes ad-
here to the sides of the tube; sometimes they form a sedi-
ment. Rarely, there is general clouding of the medium
(Streptococcus diffusus).
In mixtures of bouillon and blood-serum or ascitic
fluid the streptococcus grows much better, especially at
incubation temperatures, and in such mixtures the lux-
uriant development causes the liquid to appear clouded.
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-