Orbicularis Palpebrarum.
Corrugator Supercilii.
Levator Palpebrse.
Tensor Tarsi.

Dissection (fig.130-4). In order to expose the muscles of the face, continue the longitudinal incision made in the dissection of the Occipito-frontalis, down the median line of the face to the tip of the nose, and from this point onwards to the upper lip; another incision should be carried along the margin of the lip to the angle of the mouth, and transversely across the face to the angle of the jaw. The integument should also be divided by an incision made in front of the external ear, from the angle of the jaw, upwards, to the transverse incision made in exposing the Occipito-frontalis. These incisions include a square-shaped flap which should be carefully removed in the direction marked in the figure, as the mus-clea at some points are intimately adherent to the integument.

The Orbicularis Palpebrarum is a sphincter muscle which surrounds the whole circumference of the orbit and eyelids. It arises from the internal angular process of the frontal bone, from the nasal process of the superior maxillary in front of the lachrymal groove, and from the anterior surface and borders of a short tendon, the Tendo palpebrarum, placed at the inner angle of the orbit. The muscle, thus arising, forms a broad, thin, and flat plane of elliptical fibres, which cover the eyelids, surround the circumference of the orbit, and spread out over the temple, and downwards on the cheek, becoming blended with the Occipito-frontalis and Corrugator supercilii. The palpebral portion (ciliaris) of the Orbicularis is thin and pale; it arises from the bifurcation of the Tendo palpebrarum, and forms a series of concentric curves, which are united on the outer side of the eyelids at an acute angle by a cellular raphe, some being inserted into the external tarsal ligament and malar bone. The orbicular portion (orbicularis latus) is thicker, of a reddish colour, its fibres well developed, forming a complete ellipse.

The tendo palpebrarum (oculi) is a short tendon, about two lines in length and one in breadth, attached to the nasal process of the superior maxillary bone anterior to the lachrymal groove. Crossing the lachrymal sac, it divides into two parts, each division being attached to the inner extremity of the corresponding tarsal cartilage. As the tendon crosses the lachrymal sac, a strong aponeurotic lamina is given off from its posterior surface, which expands over the sac, and is attached to the ridge on the lachrymal bone. This is the reflected aponeurosis of the Tendo palpebrarum.

Relations. By its superficial surface, the orbicular portion is closely adherent to the integument, more especially over the upper segment of the muscle; the palpebral portion being separated from the skin by loose areolar tissue. By its deep surface, above, with the Occipito-frontalis and Corrugator supercilii, with which it is intimately blended, and with the supra-orbital vessels and nerve; below, it covers the lachrymal sac and the origin of the Levator labii superioris, Levator labii superioris alseque nasi, and the Zygomaticus major and minor muscles. Internally, it is occasionally blended with the Pyramidalis nasi. Externally, it lies on the temporal fascia. On the eyelids, it is separated from the conjunctiva by a fibrous membrane and the tarsal cartilages.

The Corrugator Supercilii is a small, narrow, pyramidal muscle, placed at the inner extremity of the eyebrow beneath the Occipito-frontalis and Orbicularis palpebrarum muscles. It arises from the inner extremity of the superciliary ridge; its fibres pass upwards and outwards, to be inserted into the under surface of the orbicularis, opposite the middle of the orbital arch.

Relations. By its anterior surface, with the Occipito-frontalis and Orbicularis palpebrarum muscles. By its posterior surface, with the frontal bone and supra-orbital vessels and nerve.

The Levator Palpebriz will be described with the muscles of the orbital region.

The Tensor Tarsi is a small thin muscle, about three lines in breadth and six in length, situated at the inner side of the orbit, beneath the Tendo oculi. It arises from the crest and adjacent part of the orbital surface of the lachrymal bone, and passing across the lachrymal sac, divides into two slips, which cover the lachrymal canals, and are inserted into the tarsal cartilages near the Puncta lachry-malia. Its fibres appear to be continuous with those of the palpebral portion of the Orbicularis; it is occasionally very indistinct.

Nerves. The Orbicularis palpebrarum and Corrugator supercilii are supplied by the facial and supra-orbital nerves; the Tensor tarsi by the facial.

Actions. The Orbicularis palpebrarum is the sphincter muscle of the eyelids. The palpebral portion acts involuntarily in closing the lids, and independently of the orbicular portion, which is subject to the will. When the entire muscle is brought into action, the integuments of the forehead, temple, and cheek are drawn inwards towards the inner angle of the eye, and the eyelids are firmly closed. The Levator palpebrae is the direct antagonist of this muscle; it raises the upper eyelid, and exposes the globe. The Corrugator supercilii draws the eyebrow downwards and inwards, producing the vertical wrinkles of the forehead. This muscle may be regarded as the principal agent in the expression of grief. The Tensor tarsi draws the eyelids and the extremities of the lachrymal canals inwards, and compresses them against the surface of the globe of the eye; thus placing them in the most favourable situation for receiving the tears. It serves, also, to compress the lachrymal sac.