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THE DECAY OF THE TEETH. 131

playing no small part in the matter; and when once the dis-
ir.cegration is established in some congenitallj defective point,
the accumulations of food and secretions in the oral cavity will
intensify the mischief by furnishing new supplies of acids." In
the last edition of Toraes's work the phrase " organisms having
no small share in the matter" takes the place of " buccal mucus
probably playing no small part in the matter."' -
Watt has also made himself conspicuous by his obstinate de-
fence of the chemical theory. He refers the diiferent colors of
carious dentine to the action of various mineral acids.
J. Taft^^ also favors the chemical theory. "Acid mucus and
saliva, vitiated secretions, products of decomposition of animal
and vegetable matter in the mouth, and galvanic action, mineral
and vegetable acids," are, in his opinion, the chief causes of
dental decay.
Schlencker^^ writes, " Dental caries is therefore a purely chemi-
cal process. Be it repeated, where there is no acid, no caries is
possible."
Baume adheres to the chemical and opposes the parasitic
theory. " Thefaivji are the result of the caries" (!)
Comparative microscopical examinations of decayed dentine
K
and dentine simply decalcified by acids, and even a macroscopic
-comparison of decayed teeth with teeth which have been acted
upon for a certain length of time by acids only, furnish sufficient
proof for the untenableness of the purely chemical theory. The
microscopic changes characteristic of decaj^ed dentine as repre-
sented in Figs. 58-88 cannot bo produced by any acid or acids.
It is not to be denied that such changes as the swellino^ or
tumefaction of the fresh or living dentinal fibrils may be brought
about by the action of acids, since all delicate organic tissues
suffer more or less change when acted upon by external agents.
But the enlargement of the dentinal tubules, the liquefaction of
the basis-substances, the confluence of the canals, and the forma-
tion of cavities in the dentine are absolutely inexplicable by the
action of acids in such a diluted state as they occur in the mouth.
By the action of sugar, as well as of various acids, ^fagitot^
succeeded in producing cavities in the dental tissues which were
very similar to those formed by decay. It is not difiicult by the