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PATHOLOGICAL CONDITIONS. 243

precipitated, and the surface is therefore exposed to
the continued action. It is preferable to employ the
nitrate in the solid state, or, when this is not practi-
cable, in a concentrated solution and small quantity,
rather than in a copious dilution and repeated appli-
cation.
From the observations already made, it is quite

evident that no harm can result to the tooth from a
proper application of this agent, beyond the portion
of it immediately acted upon. The nitrate can not
be absorbed by dentine, but it stimulates the sub-
jacent dentine to more healthy action ; though some
maintain that it is not as efficient in this respect as

some proper chlorid. It acts to a greater depth than
tannin or creosote, but not so deep as chlorid of zinc,
nor with so much pain. Great care should be exer-
cised that its contact be permitted no further than its
action is desired.
Chlorid of Zinc,—This agent has been extensively,
though much less now than formerly, used in the
treatment of sensitive dentine. It exerts an anti-
septic and disinfectant, as well as an escharotic
influence. In its operation it decomposes, the chlorine
uniting with the animal and the calcareous elements

of the dentine. It is milder in solution than in solid,
and less efficient and less painful. It is soluble in
water, alcohol, ether, or chloroform. The etherial