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PATHOLOGICAL CONDITIONS. 241

already explained. Either its aqueous or its alcoholic
solution may be employed; the latter being the better
and more convenient preparation. It is however
recently used by solution in creosote and glycerin,
which constitute very valuable preparations. Where
tannin is applied to dentine, there is formed a tannate
of albumen, which, being insoluble, protects from irri-
tation, and probably incites to healthy condition, the

living parts beneath it.
Creosote, or Carbolic Acid.—Formerly, creosote was

obtained by distillation of wood, and differed some-
what from that in present use, which is prepared by
distillation of coal tar. It dissolves freely in alcohol or
ether, and sparingly in water • its action may therefore
be modified by dilution. Creosote produces its caustic
effects by its affinity for albumen and gelatin, with

which it forms insoluble compounds ; and from its
modus operandi, it is evident that the popular opinion
that it promotes decay of the teeth is an error.
Nitrate of Silver.—This salt is a powerful caustic,
whether applied to soft parts or to bony tissue. Its
action is somewhat complex. Nitric acid is liberated
by the decomposition of the salt, when in contact with
organic matter. Nitrate of silver has a strong affinity
for albumen, uniting with it without difficulty ; and
the compound thus formed, is soluble in nitric acid.
When the nitrate is applied to the skin, the immediate