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308 THE MICRO-ORGANISMS OF THE HUMAN MOUTH.

fermentation took place an elevation of the surface of the gela-
tine was observed, due to the formation of bubbles of gas, and
in those tubes containing the smallest quantity of HCl the mix-
ture Avas in part driven quite out of the tube. I found that not
till the proportion of IICl reached 1.6 to 1000 did the surface
of the mixture remain at a constant level, or, in other words, did
the fermentation cease. Salicylic acid effected the same in the
proportion of 0.4 to 1000. If, therefore, in a food mixture we
wish to prevent fermentation, or to arrest it when once begun,
we must add 1.6 grams HCl or 0.4 gram salicylic acid to each
1000 grams of the mixture.
In the human stomach, however, we have to deal, not with a
total lack of HCl, but rather with a diminution in the quantity
of the same, so that we require only to supplement the acid
already present. When digestion is at its most active stage, the
proportion of HCl in the contents of the stomach under normal
conditions is about 2 to 1000, and since fermentation does not
take place till this proportion has been reduced to 1.6 to 1000,
we must, in cases of continued fermentation in the stomach,
suppose a lack of HCl equal to at least 0.4 gram per liter of
stomach contents, and this quantity must be administered in
order to restore tlie normal condition.
According to the determinations of Bidder and Schmidt, ten
to twenty liters of gastric juice are secreted daily. If we con-
sider this estimate as two to four times too high, and take
five liters as the real quantity, we still have ten grams HCl
(forty grams HCl solution of sp. gr. 1.1233) which are daily
poured into the human stomach. Under such circumstances we
can hardly expect to produce much impression by the three- to
ten-drop doses recommended in text-books. The quantity of
any given antiseptic which is necessary to suspend fermentation
in the human stomach depends upon the intensity of the fer-
mentation and the quantity of the stomach contents; in any
case we must calculate upon large and repeated doses of HCl
if we wish to produce a marked impression. In case of the
ordinary lactic-acid fermentation outside of the stomach the
process will, in a few hours, be retarded by the antiseptic action
of the acid wbich is produced. In the stomach this action loses