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22 THE MICRO-ORGANISMS OF THE HUMAN MOUTH.

"^tt»d- above 45^° C. all development ceases, the optimum lying-
between 35° and 42° C. It po^^sesses inverting action, and trans-
forms not onl}' dextrose, but also cane-sugar, milk-sugar, and
mannite into lactic acid. Its ferraent^ction is reguTarh' accom-
panied b}' the development of carbonic acid.
It is not improbable that this bacillus plays an essential part
in fermentations of the human mouth. The frequency of its
occurrence in the oral cavity has, however, not yet been deter-
mined, although I have several times cultivated a micro-organism
from the mouth which, in point of morphology and physiology,
seems to be identical with Hueppe's bacterium.

b. Mannite Fermentation.
Mannite fermentation (mucous or gum fermentation) is caused
by an exceedingh' small coccus (Micrococcus viscosus) which
grows in chains in various saccharine beverages, in wine, beer,
etc., and in saccharine juices. In consequence of the fermenta-
tion these liquids become slimy, viscous (stringy).
The products of fermentation are a kind of gum (viscose),
closely resembling dextrine, also mannite and carbonic acid. The
optimum of temperature is 30° C. Black-* observed a similar
fermentation, caused by the action of various mouth-bacteria
(micrococci) in saccharine solutions; One coccus, occurring in
chains, cultivated in peptone bouillon with 2 per cent, of sugar,
*' gelatinized" the fluid so entirely in twenty-four hours that it
did not run out when the tube was inverted. The optimum of
temperature was above 100° F. The products of fermentation
were not examined. This fermentation, which is most probably
a kind of gum fermentation, explains, according to Black, the
mucous coating on the teeth and tongue in case of sordes in fever.

c. Dextrane Fermentation.
Dextrane fermentation occurs spontaneously under the action
of a micrococcus, Leuconostoc mesenterioides, in the juice of the
beet and in the molasses of sugar factories, and can also be in-
duced artificially in saccharine solutions. The masses of bacteria
(zoogloea) form a jelly of cartilaginous consistency, which com-
pletely fills the vessels containing the molasses. The products