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It is asserted by a celebrated anatomist that he has con-
stantly found two holes near the point of each root, for the
admission of vessels, not only of the incisores and cuspidati,
but also of those of the grinders ; which he supposes to have
been established by nature, in order to guard against acci-
dent, lest if one vessel were injured or destroyed, the other
might continue to nourish the pulp. I confess I was never
so fortunate as to meet a single instance of this kind, even in
the incisores of large animals ; except in such cases as Eus-
tachius mentions, where he says, (speaking of the roots of
the permanent grinders,) " Many of these roots (s. c. roots,)
being flattened, their sides thus approach ; so that, instead
of a circular opening, an oblong one is formed, the central
points of whose sides coming into contact, leave at either
end a small canal." In such roots, however, I have fre-
quently found but one opening externally, for the admission
of vessels, &c. but after their entrance each divided into
two branches. Haver mentions, * that in a tooth winch had
but one root, he met two passages, one at each side. This
must have been formed in the manner Eustachius describes.
I have seen a few of the permanent incisores with almost
two distinct roots, the cuspidati with two, sometimes with
three roots, and the grinders with four and even five roots,
and of course as many openings as roots.

Ostreologia, page 79.