SOURCES, COMPOSITION, AND QUALITIES
OF IVORY
What is
ivory? We all know it as one of the most attractive art materials, but
the structural qualities to which its beauty and appropriateness are
due and the sources whence it is derived are often lost sight of by
those who fully appreciate its rare beauty when they see some artistic
object executed in this soft-toned and yet rich and lustrous material.
In its most restricted sense, the term "ivory" denotes primarily
elephant ivory, although as generally employed the designation covers
many other forms of dentine.
The
characteristic distinction between true ivory and other forms of
dentine appears on examining a transverse section, when wavy lines of
different shades are observable, their decussations enclosing minute
approximately lozenge-shaped spaces in concentric rows. Under the
microscope the tubular structure is revealed, the tubes being
exceedingly minute and closely set; their smallest branches are
immeasurably fine, while at the largest point they only average 1-1000
of an inch. Their angular gyrations are much more marked than are the
secondary curvatures of ordinary dentine; these are believed, in both
cases, to be due to successive stages of calcification. Through the
tubes pass from the central pulp excessively fine threads of a
protoplasmic substance. The disposition and the peculiar curvature of
the ivory tubes serves to render the entire
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