Page 62 - My FlipBook

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bottom of this alveolar cavity, in a slight groove, which af-
terwards becomes a complete and distinct bony canal.
The alveolar process grows with the teeth, and for some
time keeps the start of them. The ridges which are to make
the partitions shoot from the sides across the canal, at the
mouth of the cell, forming hollow arches. This change hap-
pens first at the anterior part of the jaws. As each cell be-
comes deeper, its mouth also grows narrower, and at length
is almost, but not quite, closed over the contained tooth."
" The disposition for contracting the mouth of the cell, is
chie% in the outer plate of the bone, which occasions the con-
tracted orifices of the cells to be nearer the inner edge of
the jaw. The reason, perhaps, why the bone shoots over,
and almost covers the tooth, is, that the gum may be firmly
supported before the teeth have come through.
The alveoli which belong to the adult grinders, are form-
ed in another manner: in the lower jaw they would seem to be
the remains of the root of the corbnoid process, for the cells are
formed for those teeth in the root of that process ; and in
proportion as the body of the bone, and the cells already
formed, push forwards from under that process, the succeed-
ing cells and their teeth are formed and pushed forward in
the same manner."
" In the upper jaw there are cells formed in the tubercles
for the young grinders, which at first are very shallow, and
become deeper and deeper as the teeth grow ; and they
grow somewhat faster, so as almost to enclose the whole
tooth, before it is ready to push its way through that enclo-
sure and gum. There is a succession of these, till the whole
three grinders are formed."
In the adult, the alveoli are usually from one third to
two thirds of an inch in depth, being much deeper in the
front than on the posterior part of the jaws. They are ap-