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114 HUNTER ON THE TEETH.

The Alveoli which belong to the adult Grinders, are formed
in another manner ; in the Lower-Jaw they would seem to be
the remains of the root of the Coronoid 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 succeeding 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 inclose the whole Tooth before it is ready
to push its way through that inclosure and Gum. There is a
succession of these, till the whole three Grinders are formed, (u)

enclosed teeth, which are no longer liable to fall out when the bone is
examined." At the age of six months he has found the inversion of the
edges of the alveoli, and consequent narrowing of the apertures less
pronounced. He adds, " the increased size of the alveolar orifices must
be regarded as the first of those changes which precede the eruption oi
the teeth." (1)]
(u) [At the time of birth, a large open socket exists, posterior to the
alveolus for the first temporary molar in both jaws. In the upper jaw,
this, at that time, has a very imperfect posterior wall. The rudiments
of a septum, however, intended to divide the large socket into two
alveoli, one for the second temporary, and the other for the first per-
manent molar, are present. The division of the socket usually takes
place a little earlier in the lower than in the upper jaw. At the age of
eight months, the septum between the second milk and first permanent
molar is still imperfect. In the upper jaw the posterior wall of the
crypt of the first permanent molar is in progress of development, but
not complete. At twelve months, the alveolus of the first permanent
molar in the upper jaw has become more perfect. The alveoli of these
teeth, in both jaws, communicate with the surface by small openings,
in a line with the alveoli of the other teeth. At eighteen months, "the
first permanent molars lie deep within their respective sockets, the
orifices of which, in the lower jaw, are contracted by the inversion of
the outer alveolar plate, and the base of the coronoid process, the teeth
at this time being placed with their posterior two-thirds, internal to that
portion of the jaw. The posterior edge of the socket is brought forward
(1) Tomes's 'System of Dental Surgery,' pp. 13—16.