THE CULTIVATION OF ANAEROBIC BACTERIA.
THE cultivation of micro-organisms wliich will not
grow where the least amount of oxygen is present is
always attended with much difficulty, and can seldom be
accomplished with certainty. Many methods have been
suggested, but not one can be described as satisfactory.
Koch originally cultivated anaerobic bacteria upon
plates by covering the surface of the soft gelatin with a
thin film of mica previously sterilized by incandescence.
Some anaerobic forms will grow quite well by such a
simple exclusion of the air, but the strictly anaerobic
forms will not develop at all.
Hesse originated the plan, still sometimes followed, of
making a deep puncture in recently boiled and rapidly
sterilized gelatin or agar-agar, then covering the surface
with sterilized oil, through which no oxygen was sup-
posed to penetrate (Fig. 35).
lyiborius suggested the plan of having a tube nearly
full of gelatin or agar-agar, boiling it just before inocu-
lation, so as to expand and drive out whatever air it
might contain, making the inoculation while the culture-
medium was still fluid, cooling rapidly in ice-water, and
sealing up the tube in a blowpipe as near the surface of
the gelatin as possible.
Esmarch used a regular "Esmarch tube," into the
central cavity of which melted sterile gelatin was poured
to exclude the air.
Buchner invented a method by which, by the use of
jjyrogallic acid, the oxygen was absorbed from the atmo-
sphere in which the culture was kept, and the growth
allowed to continue in the nitrogen and carbonic acid