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108 HUNTER ON THE TEETH.
mastication, we may observe, once for all, that their action and
re-action must be always equal, and that the Teeth of the
Upper and Lower-Jaws are complete, and equal antagonists
both in cutting and grinding.
When the Lower-Jaw is depressed, the Condyles slide for-
wards on the eminences ; and they return back again into the
cavities, when the Jaw is completely raised.
This simple action produces a grinding motion of the Lower-
Jaw, backwards on the Upper, and is used when we divide any
thing with our fore Teeth, or Incisores. For this purpose, the
Incisores are well formed; as they are higher than the others,
their edges must come in contact sooner ; and as the Upper
project over the Under, we find in dividing any substance with
them, that we first bring them opposite to one another, and as
they pass through the part to be divided, the Lower-Jaw is
brought back, while the Incisors of that Jaw slide up behind
those of the Upper-Jaw, and of course pass by one another.
In this way they complete the division, like a pair of scissars
and at the same time they sharpen one another. There are
exceptions to this ; for these Teeth in some people meet equally,
viz. in those people whose Fore-Teeth do not project further
from the Gum, or socket, than the back Teeth ; and such Teeth
are not so fit for dividing ; and in some people the Teeth of
the Lower-Jaw are so placed, as to come before those of the
Upper-Jaw; this situation is as favourable for cutting as when
the over-lapping of the Teeth is the reverse, except for this
circumstance, that the Lower-Jaw must be longer, and therefore
its action weaker.
The other motion of the Lower-Jaw, viz. when the lateral
Teeth are used, is somewhat different from the former. In
opening the mouth, one Condyle slides a little forwards, and
the other slides a little further back into its cavity; this throws
the Jaw a little to that side, just enough to bring the lower
Teeth directly under their corresponding Teeth in the Upper-
Jaw: this is done, either in dividing, or holding of substances;
and these are the Teeth that are generally used in the last
108 HUNTER ON THE TEETH.
mastication, we may observe, once for all, that their action and
re-action must be always equal, and that the Teeth of the
Upper and Lower-Jaws are complete, and equal antagonists
both in cutting and grinding.
When the Lower-Jaw is depressed, the Condyles slide for-
wards on the eminences ; and they return back again into the
cavities, when the Jaw is completely raised.
This simple action produces a grinding motion of the Lower-
Jaw, backwards on the Upper, and is used when we divide any
thing with our fore Teeth, or Incisores. For this purpose, the
Incisores are well formed; as they are higher than the others,
their edges must come in contact sooner ; and as the Upper
project over the Under, we find in dividing any substance with
them, that we first bring them opposite to one another, and as
they pass through the part to be divided, the Lower-Jaw is
brought back, while the Incisors of that Jaw slide up behind
those of the Upper-Jaw, and of course pass by one another.
In this way they complete the division, like a pair of scissars
and at the same time they sharpen one another. There are
exceptions to this ; for these Teeth in some people meet equally,
viz. in those people whose Fore-Teeth do not project further
from the Gum, or socket, than the back Teeth ; and such Teeth
are not so fit for dividing ; and in some people the Teeth of
the Lower-Jaw are so placed, as to come before those of the
Upper-Jaw; this situation is as favourable for cutting as when
the over-lapping of the Teeth is the reverse, except for this
circumstance, that the Lower-Jaw must be longer, and therefore
its action weaker.
The other motion of the Lower-Jaw, viz. when the lateral
Teeth are used, is somewhat different from the former. In
opening the mouth, one Condyle slides a little forwards, and
the other slides a little further back into its cavity; this throws
the Jaw a little to that side, just enough to bring the lower
Teeth directly under their corresponding Teeth in the Upper-
Jaw: this is done, either in dividing, or holding of substances;
and these are the Teeth that are generally used in the last
