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AREOLAR TISSUE, TENDONS, AND MUSCLES. 187

occasionally only one belly is present, or the anterior belly is sometimes
fused with the sterno-hyoid muscle.
Action.—It depresses and carries the hyoid bone backward ; it is also
a tensor of the cervical iascia.

THE MUSCLES OF THE SUPRA-HYOID SPACE.
The muscles of the supra-hyoid space (Fig. 95) are the digastric,
stylo-hyoid, mylo-hyoid, genio-hyoid, genio-glossus, lingualis, hyo-
glossus, and stylo-glossus.
The Digastric, as its name implies, is a double-bellied muscle, one
posterior and one anterior, extending from the mastoid portion of the
temporal bone to the anterior part of the lower jaw. The posterior belly

Fig. 95.

Muscles of the Tongue, left side.
is the longer and narrOM^er of the two, and arises from the digastric
groove of the temporal bone, close to the stylo-mastoid foramen ; pass-
ing downward, forward, and inward, it gradually diminishes as it
approaches the hyoid bone, and is lost in a tendon which usually
passes through the stylo-hyoid muscle near its insertion, and also
.
through its aponeurotic loop, which is lined by a synovial membrane,