They are of a different texture, the laminae
more loosely combined, and possessing a tendency to separate, which
renders them unfit for nearly all useful purposes. Ivory has the same
chemical constitution as ordinary teeth--that is, cartilage united to
such earthy ingredients as the phosphate of lime.
But it is very remarkable that the fossil ivory of the mammoth, and
specimens of the historic period of Pompeii or Egypt, contain
sometimes as much as 10 per cent. more of fluoride of calcium than the
ivory of the present day. We apprehend, however, that this
property--first investigated by Dr George Wilson--may be derived from
long-continued contact with earth, since fluoride of calcium is the
chief ingredient in the enamel or exterior portion of the tooth.
Ancient ivory, having thus gained in its inorganic bases, becomes
deficient in the gelatinous constituents necessary to its
preservation. We recently had a singularly beautiful application of
the knowledge of this principle in the case of the ivory specimens
sent from Nineveh by Mr Layard. On their arrival in England, it was
discovered that they were rapidly crumbling to pieces. Professor Owen
recommended that the articles should be boiled in a solution of
albumen, which was done accordingly, and the ivory rendered as firm
and solid as when it was first entombed.
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