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MOUTH-bACTERIA AS EXCITERS OF FERMENTATION. 113

3. The Arctic Add Fermentation

certainly does not occur in the oral cavity, for the simple reason
that this fermentation cannot take place at a higher temperature
than 35° C. ; hesides, the necessary quantity of alcohol and of
acid essential to this fermentation is wanting. Escherich^ dis-
covered in the intestinal tract of a child a micro-organism called
by him Bdrtcrium lactis aerofjeucs, to which he ascril)cs the pure
lactic acid fermentation. According to Baginsky,"^ however, it
develops only minute cpiantities of lactic acid and profuse ([uan-
tities of acetic acid. Xothing is known as to its occurrence
in the mouth. Among seven of the hacteria which Vignal ex-
amined, he found one which brought aliout a fermentation of
carbohydrates, by which, in addition to other products, alcohol
and carbonic acid were formed.

4. Diastatir Actio)) 3Iotith-B'/cterici.
<>f
The l)acteria wliieh I examined very seldom displayed a dias-
tatic action. Indeed, out of nine different kinds I found but
one possessing a pronounced saccharitying action. This bacte-
rium formed ti'om starch a kind of sugar having the power of
reducing the oxide of copper, and then further decomposed the
same under development of an acid reaction. It is frerpu'utly
asserted that a bacterium possesses a diastatic action, simply be-
cause it grows on slices of l)oiled potato. This assumption,
however, is inadmissilde, inasmuch as the micro-organisms are
by no means restricted to the potato starch alone, but may also
derive nourishment from tlie albumen, sugar, etc., of the potato.

5. Inrertin(I Action of Moath-Bactcrict.

Cane-sugar, Ci2H220,i (which is unfermentable, does not reduce
oxide of copper ii^^ alkaline solutions, and turns the plane of
polarization to the right), treated with a ferment, soluble in
Avater and contained in beer-yeast, higher }>lants, and apparently
also in many fungi, will, on the addition of water, l)e converted
into invert-sugar. The latter is a mixture of grape- and fruit-