Part 23

Origin on the ligament which connects the zygomatic process of the frontal with the frontal process of the malar. The fibres form a thin band about 7 millimeters wide which passes craniad, closely united to the inner surface of the frontoscutularis. At the caudal edge of the zygomaticus (d) the muscle is interrupted by a short tendinous interval; the fibres then continue to their insertion on the tip of the antitragus.

Relations.--Outer surface with the frontoscutularis, the zygomaticus (d), and the integument. Inner surface with the temporal muscle and M. antitragicus (n).

Action.--Pulls the ear craniodorsad.

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The remainder of the muscles of the ear, which, with the exception of the tragicus lateralis, merely interconnect the cartilages of the external ear or parts of these cartilages, are described in connection with the account of the Auditory Organ.

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Owing to the presence of the fibrous pad to which the whiskers are attached, the facial muscles between the eye and the mouth differ in the cat in some respects from those of related animals. This fibrous pad interrupts the muscles, frequently breaking muscles which are elsewhere single into two.

=M. zygomaticus minor=, or malaris (Fig. 64, e).--This muscle is not always present; when it exists it forms a very thin flat band of fibres passing from the ventral side of the eye toward the angle of the mouth.

Origin among the fibres of the orbicularis oculi (s) in the lower eyelid. The fibres pass ventrad; the insertion varies. In some specimens the insertion is among the fibres of the orbicularis oris (i), at the angle of the mouth, beneath the zygomaticus (d). In other cases this muscle is said to be inserted into the pad on which the whiskers rest.

Relations.--Outer surface with the integument and near its insertion with the zygomaticus major (d). Inner surface with the malar bone and the masseter muscle.

Action.--Pulls the angle of the mouth (or the whiskers) dorsad.

=M. orbicularis oris= (Fig. 64, i).--This forms a very thin layer of subcutaneous concentric fibres which surround the mouth, that of the upper lip being thicker than that of the lower lip. The part of the muscle in the lower lip has its fibres intermingled with those of the platysma (a′). In the median line the fibres of the upper lip are interrupted by a raphe, and caudad of this are intermingled with those of the caninus.

=M. quadratus labii superioris= (Fig. 63, p and q; Fig. 64, f and g).--This is a complex of muscle-fibres attached chiefly to the fibrous pad on which the whiskers rest. In it two parts can be distinguished more or less completely.

(1) =M. levator labii superioris alæque nasi= (Fig. 63, p; Fig. 64, g) on the sides of the nose. This arises (a) as a continuation of the frontal portion of the epicranius, and (b) in a small bundle (Fig. 63, p) from near the dorsal end of the frontal process of the maxillary bone, in common with the next. The two slips thus formed unite craniad and are inserted partly into the integument on the outer side of the wing of the nose, partly into the skin of the upper lip, lateroventrad of the nose, and partly into the pad on which the whiskers are located, in connection with the next.

(2) The =angular= head (=caput angulare=), or =levator labii superioris proprius= (Fig. 63, q; Fig. 64, f) is much larger than the last. It takes origin from a small tubercle at the cranial border of the orbit, close to the origin of the orbicularis oculi. The fibres diverge from their origin to their insertion among the whiskers and in the fibrous pad on which the whiskers rest.

Action.--Erects the whiskers and raises the upper lip.

=M. caninus= or =levator anguli oris= (Fig. 64, f′).

Origin in a depression on the lateral surface of the maxillary bone, just craniad of the last premolar tooth. The fibres pass craniad, diverging, toward the whiskers, and have their insertion into the pad of tissue on which the whiskers rest.

Action.--Retracts the whiskers and raises the upper lip.

=M. buccinator.=--A thin muscle against the mucous membrane of the upper lip, partly united with the orbicularis oris and lying beneath M. caninus.

Origin on the outer surface of the superior maxillary bone in the depression between the infraorbital foramen and the first premolar tooth. The fibres pass ventrad, diverging, and mingle with those of the deep part of the orbicularis oris.

Relations.--Outer surface with the caninus and with the orbicularis oris. Inner surface with the mucous membrane of the upper lip.

Action.--Raises the upper lip.

=M. myrtiformis= (probably corresponds to a part of the human M. nasalis) (Fig. 64, h).--A thin sheet of muscle-fibres lying craniad of the levator labii superioris alæque nasi and passing from the whiskers to the nose and upper lip. It is distinguishable from the alæque nasi by the direction of the fibres.

Origin from the pad upon which the whiskers rest. The fibres diverge and have their

Insertion upon the wing of the nose and into the skin of the upper lip near the median line.

Action.--Dilator of the nares and elevator of the upper lip.

=M. “moustachier”= (Str.-D.) (probably corresponds to one of the Mm. incisivi).--It lies on the upper lip near the median line.