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306 THE MICRO-ORGANISMS OF THE HUMAN MOUTH.

brought into small flasks, sterilized, and then infected, some
with a very sensitive vibrio, the others with hardy ferment-bac-
teria from the stomach. To each portion was now added, every
ten minutes, 2.0 cc. of an artificial gastric juice containing 0.4
per cent. HCl (1.6 cc. HCl solution of sp. gr. 1.1233), so that,
at the end of the second hour, the mixtures contained each
0.2 per cent. HCl, corresponding to the most active point of
normal gastric digestion, which has been determined to be at
about the end of the second hour or a little later, when the
acidity of the stomach has reached its highest degree. Cultures
made from time to time, during the course of the experiments,
from the diiFerent flasks showed that the least resistant of the
micro-organisms experimented with retained their vitality till
the end of the third half-hour, sometimes even longer, and that
the less sensitive ferment-bacteria showed no diminution in
number at the end of the experiment, and in many cases some
of them were still found six to eight hours later. Inasmuch as
portions of food pass into the duodenum in less than half an hour
after entering the stomach, these experiments seem to indicate
that any micro-organism swallowed at the beginning of a meal
might readily pass through the stomach alive. The case is some-
what diflferent, however, if the bacteria are swallowed when the
digestion is at its most active stage (second and third hour). Ex-
periments representing this stage of digestion showed that very
sensitive putrefactive bacteria may thus be destroyed within
ten minutes, while the hardiest ferment-bacteria may resist for
hours.
" From these experiments the conclusion appears warranted
that all bacteria which are swallowed at the beginning of a meal
may pass alive into the intestines, while of such as are swallowed
in the second or third hour, only those which are less sensitive to
the action of acids retain their vitality. If we furthermore take
into consideration the various and numerous affections in which
the quantity of gastric juice or its percentage of HCl is abnor-
mally small, it will appear as though the stomach affords almost
no protection whatever against the entrance of pathogenic organ-
isms into the intestinal canal, and that the condition of the
intestines themselves must be looked upon as the factor which