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BONES. 115
The Inferior Synovial Sac is situated betM'een the cartilage and the
condyle.. It extends on the condyle posteriorly to a greater extent than
it does anteriorly.
The Internal Lateral Ligament is not directly connected with the
temporo-maxillary articulation, but acts as an accessory ligament to the
joint. It is a fascia-like band extending from the spinous process of
the sphenoid bone; becoming broader as it descends, it is inserted into a
triangular process of bone on the anterior border of the posterior dental
foramen. The external pterygoid muscle crosses the superior portion
of this ligament externally, the internal maxillary artery and the infe-
rior dental vessels and nerve passing lower down between the ligament
and the bone.
The Stylo-maxillary Ligament is the other accessory ligament of the
temporo-maxillary articulation. It is a strong fibrous band connected
with the deep cervical fascia, extending from a point in close proximity
to the apex of the styloid process of the temporal bone to the inferior
portion of the posterior border of the ramus of the jaw, where it is
inserted between the masseter muscle externally and the internal ptery-
goid muscle internally. The stylo-maxillary ligament divides the
parotid from the submaxillary region, and is connected by fasciculi
with the stylo-glossus muscle.
The movements permitted by the temporo-maxillaiy articulation are
more varied and of greater number than those of any joint in the body.
it can be depressed
The jaw has the power of extension and retraction ;
and elevated, moved from side to side, and combines all the movements
intermediate between these, thus allowing the gliding motion necessary
to mastication. The interarticular hbro-cartilage assists in these varied
movements and acts as a multiplier of them. The superior surface. of
this cartilage glides forward on to the articidar eminence of the anterior
root of the zygoma, while the condyle of the inferior maxilla rotates
on a transverse axis in the concavity of the inferior surface of this
cartilage. When the mouth is widely opened the cartilages of each
articulation move forward on to the articular eminence, the condyles
being carried upward on the lower surfaces of these cartilages. If the
inferior maxilla is drawn forward, so that the lower incisor teeth are in
advance of the upper ones, the action of this articulation is restricted
to a gliding of the superior surface of the interarticular cartilage over
the anterior root of the zygoma.
If the lower jaw is too much depressed, as is sometimes the case in
"yawning, vomiting, the extraction of the teeth, or as the result of blows,
dislocation will follow. This luxation is caused by the interarticular
cartilage being carried forward to the eminence on one or both sides,
or by one of the condyles of the inferior maxilla breaking through the
anterior portions of the capsular ligament, its weakest point, and lodg-
ing in the zygomatic fossa.

Sutures.
The bones of the skull, ^vith the exception of the inferior maxilla and
temporal bones and the cartilaginous bones at the base of the skull, are