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simple than that of the others, there is in general only one
shell formed, but on the grinders several of them appeal'.
On the anterior or small grinders, there are four shells form-
ed, sometimes however but two. On the posterior or large
grinders there are in general five shells, of which, in the un-
der jaw, three are placed externally or next the cheek, and
In the upper jaw, they are so situated that
two internally.
their eminences are adapted to the hollows of the opposite
teeth in the under jaw. As ossification advances, the bases
of these shells come in contact, and at length unite, so as to
form one shell, after which ossification proceeds for some
time, as in the incisores and cuspidati, gradually extending
over the greater part of the pulp ; and when so far advanced
as to form the body of the tooth, it begins to contract from
without, thus shaping the neck, from which the root or roots
are to commence.
As the bone of the tooth increases in thickness, the pulp
is proportionally diminished, and seems as it were converted
into bone ; its connexion however with the bony part is very
slight, except at its extreme elastic edge, so that when the
membrane surrounding the tooth is cut open, the shell can be
taken from off the pulp, without any apparent violence ; in-
deed without altering the shape of the pulp, or scarcely its
connexion with the vessels. When the shell is removed, the
pulp appears covered with a very delicate membrane, on
which the vessels form a net-work. This seems to be a
propagation of the periosteum which enters the cavity of the
jaw, along with the vessels, and probably from whence are
derived the bony lamellae of which a tooth consists.
Though this membrane is so slightly connected with the in-
ternal part of the shell, I cannot think Mr. Hunter's assertion
warrantable, when he says, " nor are there any vessels going