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812 DESTAL CARIES.

absolutely free from error. The experiment is attended with more diffi-
culties than are at first sight apparent ; especially does the sterilization
of the tilling materials themselves involve much time and labor, and the
results are not always constant ; this was especially the case with iodo-
form cement. Amalgams and phosphates gave quite constant results.
The tests with some of the materials were made over twenty-five
times ; with others, such as copper amalgams, where there was no
doubt as to the result, only a few experiments were made.
Caries of the teeth, except in the later or last stage, is the result of a
ferment process, and the organisms found in the deeper parts of decay-
ing dentine, which I have isolated and obtained in pure culture, are fer-
ment organisms. The decomposition of the pulp and contents of the
root-canal, attended by bad-smelling products, is, on the other hand, a
putrefactive process in which entirely different species of fungi are con-
cerned. Whether or not the results which I have obtained for the fungi
of caries would apply equally well to those putrefactive fungi is a ques-
tion which can be settled only by experiment upon pure cultures of the
same.
Although I have now, as I think will be granted, established upon a
sure basis the fact that caries of the teeth may result directly from the
action of acid-producing fungi in the presence of fermentable carbo-
hydrates, the conclusion would hardly be justifiable that by keeping
the mouth constantly and perfectly free from all fermentable substances,
or by repeated application of antacids or antiseptics to all parts of the
teeth, or by all these means together, we could ever banish dental caries
from the oral cavity. A most powerful influence which we do not well
understand is exerted by the nutritive processes in the teeth themselves.
I am assured by men who have grown old in the practice of dentistry
that mouths which have long been under their observation, and which
practically have been completely free from caries for years, at once, on
account of some sudden change of health, show a general breaking down
or crumbling of the teeth en masse in the space of a few weeks. It has
also been my ex])erience that ]iatients Avho have been dismissed by their
dentists in America with the assurance that, according to previous expe-
rience, their dentures Mould require no treatment for one or two years,
have come to me a few weeks later with teeth looking as though they
had not been under the hands of a dentist for years. Some say the
ocean-voyage spoiled their teeth others attribute it to a change in
;
the climate, food, health, etc.
At any rate, we have here a cause which lies without the domain of
both bacteria and acids (either ferment or otherwise). The lime salts of
the teeth are supposed to form with the organic matter of the tooth a
definite chemical compound, and it is probal)ly due to this fact that sim-
ple salts of lime are so nnich more readily soluble in weak acids than
pulvcri/X'd tooth-})one, or tiiat the tartar upon the teeth is so much more
easily soluble than the teeth themselves ; so that when any one rinses
his mouth with vinegar, and afterward finds lime in the vinegar, we
know that the lime in by far the greater part—if, indeed, we may not
say altogether—came from the tartar. Now, though there is no posi-
tive evidence for the supposition, it is cei*tainly not altogether improb-