The Ceylon sportsman, in shooting elephants, aims at a spot just above
the proboscis. If he fires a little too low, the ball passes into the
tusk-socket, causing great pain to the animal, but not endangering
its life; and it is immediately surrounded by osteo-dentine. It has
often been a matter of wonder how such bodies should become completely
imbedded in the substance of the tusk, sometimes without any visible
aperture; or how leaden bullets become lodged in the solid centre of a
very large tusk without having been flattened, as they are found by
the ivory-turner.
The explanation is as follows: A musket-ball aimed at the head of
an elephant may penetrate the thin bony socket and the thinner
ivory parietes of the wide conical pulp-cavity occupying the
inserted base of the tusk; if the projectile force be there spent,
the ball will gravitate to the opposite and lower side of the
pulp-cavity. The pulp becomes inflamed, irregular calcification
ensues, and osteo-dentine is formed around the ball. The pulp
then resumes its healthy state and functions, and coats the
osteo-dentine enclosing the ball, together with the root of the
conical cavity into which the mass projects, with layers of normal
ivory. The hole formed by the ball is soon replaced, and filled
up by osteo-dentine, and coated with cement. Meanwhile, by the
continued progress of growth, the enclosed ball is pushed forward
to the middle of the solid tusk; or if the elephant be young, the
ball may be carried forward by growth and wear of the tusk until
its base has become the apex, and become finally exposed and
discharged by the continual abrasion to which the apex of the tusk
is subjected.--_Professor Owen._