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MOLTH-BACTERIA AS EXCITERS OF FERMESTATJOy. 103
faction of organic substances is altogether impossible. Others,
again, settle the question in a manner which they think should
be satisfactory to every one by the stereotyped assertion, ''Bac-
teria are not the cause, but the result of fermentation."
Wlioever is at all versed in the fundamental principles of
bacteriology will regard it as a matter of course that the process
of fermentation going on in the oral cavity otfers no exception
to the rule that all fermentative and putrefactive processes are
conditioned by the presence of living micro-organisms. This
fact may be established experimentally by the following simple
tests
£.rp. 1. Add 2 per cent, of sugar or starch to ti'esh saliva,
and keep the mixture at blood temperature. It invariably be-
comes acid in four to live hours ; or till a glass tube two cm.
long and three mm. wide with starch, sterilize it, and fiisten it to
a molar tooth in the mouth on going to bed ; next morning the
contents of the tube will have a strong acid reaction. A cavity
in a tooth, or a piece of linen, which may be saturated Avith a
solution of starch, will answer the purpose as well as the glass
tube.
Erp. 2. Keep the mixture of saliva with starch or sugar for
one hour in the sterilizer at 100° C, and then place it in the in-
cubator ; it does not become sour in four, nor in twenty-four
hours ; in fact, not at all. TVe conclude that the agent which
caused the mixture in 1 to become sour (i.e., the ferment) is
rendered inactive by a temperature of 100° C.
Exp. 3. Heat the starch alone to 150° C. before mixing with
the saliva ; the solution still becomes sour. Heat the saliva alone,
and the mixture does not become sour. Conclusion : the ferment
exists, not in the starch, but in the saliva.
We have now to determine the question, Is it an organized
ferment (micro-organisms), or is it an unorganized ferment
(ptyaline)?
This question is determined by the following experiments:
JExp. 4. From six to eight grams of saliva are agitated in a
test tube with as much sulphuric ether as it will take u[t, starch
added, and the whole put in the inculiator. On examination
after a few hours, we will find suu'ar in the solution, but no acid ;
MOLTH-BACTERIA AS EXCITERS OF FERMESTATJOy. 103
faction of organic substances is altogether impossible. Others,
again, settle the question in a manner which they think should
be satisfactory to every one by the stereotyped assertion, ''Bac-
teria are not the cause, but the result of fermentation."
Wlioever is at all versed in the fundamental principles of
bacteriology will regard it as a matter of course that the process
of fermentation going on in the oral cavity otfers no exception
to the rule that all fermentative and putrefactive processes are
conditioned by the presence of living micro-organisms. This
fact may be established experimentally by the following simple
tests
£.rp. 1. Add 2 per cent, of sugar or starch to ti'esh saliva,
and keep the mixture at blood temperature. It invariably be-
comes acid in four to live hours ; or till a glass tube two cm.
long and three mm. wide with starch, sterilize it, and fiisten it to
a molar tooth in the mouth on going to bed ; next morning the
contents of the tube will have a strong acid reaction. A cavity
in a tooth, or a piece of linen, which may be saturated Avith a
solution of starch, will answer the purpose as well as the glass
tube.
Erp. 2. Keep the mixture of saliva with starch or sugar for
one hour in the sterilizer at 100° C, and then place it in the in-
cubator ; it does not become sour in four, nor in twenty-four
hours ; in fact, not at all. TVe conclude that the agent which
caused the mixture in 1 to become sour (i.e., the ferment) is
rendered inactive by a temperature of 100° C.
Exp. 3. Heat the starch alone to 150° C. before mixing with
the saliva ; the solution still becomes sour. Heat the saliva alone,
and the mixture does not become sour. Conclusion : the ferment
exists, not in the starch, but in the saliva.
We have now to determine the question, Is it an organized
ferment (micro-organisms), or is it an unorganized ferment
(ptyaline)?
This question is determined by the following experiments:
JExp. 4. From six to eight grams of saliva are agitated in a
test tube with as much sulphuric ether as it will take u[t, starch
added, and the whole put in the inculiator. On examination
after a few hours, we will find suu'ar in the solution, but no acid ;
