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from the one to the other.* He might as well have denied
the existence of vessels in the crystaline lens, as it more
readily slips out of its capsula, than this pulp from its shell.
As the pulp has originally no process answering to the
root or roots, it has been supposed that it is lengthened, or
squeezed out so as to form them, according as the cavity in
the body of the tooth is filled up by the ossification.! I
have already mentioned that the pulp at first assumes little
more than the size of the upper part of the body of the
tooth, which is to be afterwards formed upon it ; but it is
deposited and extends in proportion, as ossification advances.
It is the pulp and its vessels which give a determinate shape
and size to the body of the tooth, and it will in its proper
place be shown that its processes determined the size and
shape of the roots. How it is possible that the simple
fill-
ing up of the cavity in the shell of a grinder, could occasion
the pulp to lengthen out into two, three, and sometimes four
roots ?
Of those teeth which are to have but one root, the pulp
increases in length as I have described, becoming more and
more contracted towards the point ; and as ossification ad-
vances, the bone forms on it a kind of conical tube. But,
in those teeth which are to have more than one root, a beau-
tiful process is carried on. In the grinders of the lower
jaw, which in general have but two roots, the pulp is divided
into so many processes a little below the neck : at this period
there is but one general opening in the shell, from the oppo-
site sides of the edge of which, osseous fibres or little bars
shoot across, through the division of the pulp ; these meet
and unite in the middle, and so divide the cavity of the shell
into two openings, forming over it a little arch. In the grind-

Nat. Hist, page 89. t Nat. Hist, page 90,