PATHOGENIC BACTERIA.

which remained (Fig. 36). His method was to place the
tube which had been inoculated in a much larger outer
test-tube containing alkaline pyrogallic acid. The large

FIG. 35. — Hesse's
method of making
anaerobic cultures.

FIG. 36.—Buchners
method of making an-
aerobic cultures.

FIG. 37.—Frankel's meth-
od of making anaerobic cul-
tures.

tube was closed with a rubber cap, and the absorption of
the oxygen allowed to progress.

Gruber, instead of absorbing the oxygen as Buchner
does, prefers to use an air-pump and exhaust the contents
of the tube. He uses a tube having a slender neck and
a perforated rubber stopper. After the inoculation is
made the air is pumped out and the slender neck sealed
in the blowpipe. After this the tube can be warmed and
the melted gelatin or agar-agar rolled on its sides, as sug-
gested by Esmarch, if desired.

Better than any of the preceding is the method of
Frankel, which removes th$ air and replaces it by hy-
drogen. Frankel prepares an ordinary Esmarch tube,
removes the cotton stopper, and replaces it by a carefully
sterilized rubber cork containing two tubes (Fig. 37). The