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MICROSCOPICAL PHENOMENA OF DECAY. 171
of secondary enamel-decay, until an opening is formed through/
which they escape. The bacteria directly participate in the pro-/
cess, inasmuch as they invade the broken-down enamel, perhaps
drive the prisms farther apart, and destroy the remnant of organic
matter. Micro-organisms do not exert a direct influence on nor
mal enamel ; their action upon the enamel in the first stage oi
decay is therefore indirect,—that is, they act by means of the acid; \
which they produce. In the later stages of the process they exer
also a direct action upon the diseased tissue.
3. Decay of Dentine.
a. Preparation of Spenmens.
Various methods have been employed to prepare specimens
of decayed dentine for microscopic examination. In the first
place, ground sections of the decayed and the adjacent normal
dentine have been made, in the difi:erent manners described
for preparing sections of decayed enamel. Whoever has tried to
grind softened dentine or any soft tissue will easily understand
how diflicult it is to obtain good specimens in this manner. Better
sections might, perhaps, be prepared by previously hardening the
decayed matter in absolute alcohol.
A method of grinding soft tissue, or a combination of soft and
hard tissue, which v. Koch applied in the case of mollusks, has
been employed by Weil"^ for grinding the soft tissues of the
teeth. AVeil first placed the tissue (2-5 mm. thick sections of
the root or crown) into Miiller's fluid, in order to fix the soft
parts, which requires six to seven weeks. The objects were then
thoroughlj' washed, and successively brought into a 30 per cent.,
50 per cent., and finally 70 per cent, solution of alcohol to be
hardened. They were then cut into smaller pieces by a fine
bracket-saw% so as to facilitate the action of the coloring-matter
in the subse(|^uent staining process, and again placed for some
time in a 70 per cent, solution of alcohol. He then stained
them, extracted the water by means of alcohol, clearing them
up in oil of cloves; the objects were then taken out of the oil,
rinsed in pure xylol, and placed for at least twenty-four hours
MICROSCOPICAL PHENOMENA OF DECAY. 171
of secondary enamel-decay, until an opening is formed through/
which they escape. The bacteria directly participate in the pro-/
cess, inasmuch as they invade the broken-down enamel, perhaps
drive the prisms farther apart, and destroy the remnant of organic
matter. Micro-organisms do not exert a direct influence on nor
mal enamel ; their action upon the enamel in the first stage oi
decay is therefore indirect,—that is, they act by means of the acid; \
which they produce. In the later stages of the process they exer
also a direct action upon the diseased tissue.
3. Decay of Dentine.
a. Preparation of Spenmens.
Various methods have been employed to prepare specimens
of decayed dentine for microscopic examination. In the first
place, ground sections of the decayed and the adjacent normal
dentine have been made, in the difi:erent manners described
for preparing sections of decayed enamel. Whoever has tried to
grind softened dentine or any soft tissue will easily understand
how diflicult it is to obtain good specimens in this manner. Better
sections might, perhaps, be prepared by previously hardening the
decayed matter in absolute alcohol.
A method of grinding soft tissue, or a combination of soft and
hard tissue, which v. Koch applied in the case of mollusks, has
been employed by Weil"^ for grinding the soft tissues of the
teeth. AVeil first placed the tissue (2-5 mm. thick sections of
the root or crown) into Miiller's fluid, in order to fix the soft
parts, which requires six to seven weeks. The objects were then
thoroughlj' washed, and successively brought into a 30 per cent.,
50 per cent., and finally 70 per cent, solution of alcohol to be
hardened. They were then cut into smaller pieces by a fine
bracket-saw% so as to facilitate the action of the coloring-matter
in the subse(|^uent staining process, and again placed for some
time in a 70 per cent, solution of alcohol. He then stained
them, extracted the water by means of alcohol, clearing them
up in oil of cloves; the objects were then taken out of the oil,
rinsed in pure xylol, and placed for at least twenty-four hours
