assertion
being made by some chemists that by combination with the saliva a
soluble Sulphocyanide of the metallic Gold (when made the basis of
false teeth within the mouth) is produced, the important question
naturally presents itself, may not the constant chemical action thus
going on from day to day, (together with absorption of its products by
the mucous membrane within the mouth,) exercise a prejudicial effect
insidiously on the health of sensitive persons, thus morbidly
undermining the same, whilst the latent cause altogether escapes
suspicion ? Indisputably, too, there is almost a certainty that the
table-salt eaten with food, (such table-salt being a compound of
chlorine and sodium,) will act chemically on the metallic Gold of the
teeth-setting, and will form in this way persistently a daily measure
of injurious soluble Chloride of Gold during mastication of the meal.
Dentists
likewise employ another metal—Zinc, the phosphate,—as a filling powder,
for stopping cavities in carious teeth ; the calcined oxide of Zinc,
when pulverized, is mixed with crystals of, (or fluid) glacial
phosphoric acid, so as to make a stuffing which presently hardens
within the dental cavity, being applied along its floor.
It
may be thought straining the point beyond probability, almost beyond
possibility, to suppose that the Zinc in this minute quantity, and
solid form, can slowly, in a subtle manner, undermine the health of any
person within whose mouth, and subject to a minimum amount of
continuous absorption, are teeth (one, or more) which have been thus
stopped. And yet it has been experimentally ascertained that the Oxide
of Zinc, taken in doses all but inappreciable, for
