Page 45 - My FlipBook
P. 45
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the condyles forwards and backwards, the moveable cartila-
ges do not accompany the condyles in the whole extent of
their motion ; but only so far as to adapt their surfaces to the
different inequalities of the temporal bone : for as these car-
tilages, are hollow on their lower surfaces where they re-
ceive the condyle, and on their opposite upper surfaces are
convex where they lie in the cavity, but forwards, at the
root of the eminence, that upper surface is a little hollowed,
if they accompanied the condyles through the whole extent
of their motion, the eminences would be applied to the emi-
nences, the cavities would not be filled up, and the whole
articulation would be rendered very insecure.
This account of the motion of the lower jaw, and its car-
tilages, clearly demonstrates the utility of these cartilages
namely, the security of the articulation ; the surfaces of the
cartilages accomodating themselves to the different inequali-
ties, in the various and free motions of this joint. This car-
tilage is also very serviceable for preventing the parts from
being hurt by the friction ; a circumstance necessary to be
guarded against, where there is so much motion. Accord-
ingly, I find this cartilage in the different tribes of carniver-
ous animals, where there is no eminence and cavity, nor
other apparatus for grinding, and where the motion is of the
true ginglimus kind only.
In the lower jaw, as in all the points of the body, when
the motion is carried to its greatest extent, in any direction,
the muscles and ligaments are strained and the person made
uneasy. The state, therefore, into which every joint most
naturally falls, especially when we are asleep, is nearly in
the middle between the extremes of motion ; by which
means all the muscles and ligaments are equally relaxed.
Thence it is. that commonly, and naturally the teeth of the
43
the condyles forwards and backwards, the moveable cartila-
ges do not accompany the condyles in the whole extent of
their motion ; but only so far as to adapt their surfaces to the
different inequalities of the temporal bone : for as these car-
tilages, are hollow on their lower surfaces where they re-
ceive the condyle, and on their opposite upper surfaces are
convex where they lie in the cavity, but forwards, at the
root of the eminence, that upper surface is a little hollowed,
if they accompanied the condyles through the whole extent
of their motion, the eminences would be applied to the emi-
nences, the cavities would not be filled up, and the whole
articulation would be rendered very insecure.
This account of the motion of the lower jaw, and its car-
tilages, clearly demonstrates the utility of these cartilages
namely, the security of the articulation ; the surfaces of the
cartilages accomodating themselves to the different inequali-
ties, in the various and free motions of this joint. This car-
tilage is also very serviceable for preventing the parts from
being hurt by the friction ; a circumstance necessary to be
guarded against, where there is so much motion. Accord-
ingly, I find this cartilage in the different tribes of carniver-
ous animals, where there is no eminence and cavity, nor
other apparatus for grinding, and where the motion is of the
true ginglimus kind only.
In the lower jaw, as in all the points of the body, when
the motion is carried to its greatest extent, in any direction,
the muscles and ligaments are strained and the person made
uneasy. The state, therefore, into which every joint most
naturally falls, especially when we are asleep, is nearly in
the middle between the extremes of motion ; by which
means all the muscles and ligaments are equally relaxed.
Thence it is. that commonly, and naturally the teeth of the
