Part 87

Relations.--This muscle lies between the temporal muscle and the concha.

Action.--Pulls the ear ventrad and probably rotates it outward.

(b) The following three muscles connect the scutiform cartilage with other parts of the external ear.

=M. rotator auris= or =scutuloauricularis inferior=.--A flat craniocaudal band of fibres lying between the auricle and the temporal muscle.

Origin on the scutiform cartilage, just caudad of the insertion of the frontoscutularis, of which this muscle seems to be a continuation. The muscle passes caudad as a band seven or eight millimeters wide, curving about the medial surface of the auricle, and is inserted on the caudomedial surface of the eminentia conchæ.

Relations.--Lateral surface with the auricular cartilage; medial surface with the temporal muscle.

Action.--Rotates the external ear mediad and caudad.

a-i, as in Fig. 168. 1, M. adductor auris superior (cut); 2, M. adductor auris medius (cut); 3, M. helicis; 4, M. tragicus lateralis (cut); 5, 5′, M. tragicus medialis; 6, M. antitragicus; 7, M. adductor auris inferior (cut); 8, M. depressor conchæ (cut); 9, M. conchæus externus; 10, part of M. auricularis externus; 11, M. abductor auris longus (cut).]

=M. adductor auris superior= (Fig. 169, 1; Fig. 63, f). (Part of the auricularis anterior of man.)

Origin on the dorsal surface of the scutiform cartilage for its entire length. The fibres form a continuation of those of the frontoscutularis; they pass dorsocaudad and are inserted into the spina helicis or craniomedial margin of the auricular cartilage. This muscle lies in the fold of skin that connects the craniomedial angle of the auricular cartilage with the head, so that it is covered on both sides by integument.

Action.--Draws the auricle craniad.

=M. adductor auris medius= (Fig. 169, 2). (Part of the auricularis anterior of man.)--A very thin band of fibres eight to ten millimeters broad.

Origin on the middle two-thirds of the caudoventral edge of the scutiform cartilage. The fibres pass nearly ventrad and are inserted along the medial or caudal surface of the tragus.

Relations.--Outer surface with the auricular cartilage. Inner surface with the temporal muscle or with the pad of fat separating this from the auricle.

Action.--Pulls the concha dorsocraniad.

(c) The remainder of the muscles of the ear interconnect parts of the auricular cartilage.

=M. transversus auriculæ= (Fig. 63, i).--A band about six to eight millimeters wide, on the medial convex surface of the auricle, between the distal ends of M. levator auris longus (g′) and M. auricularis superior (k).

Origin on the medial surface of the concha, just proximad of the furrow which corresponds to the antihelix. The muscle bridges this furrow, passes distad about two centimeters, and is inserted on the auricular cartilage on a line which forms a caudal continuation of the line of insertion of the levator auris longus (g′).

Relations.--Outer surface with the levator auris longus (g, g′), the auricularis superior (k), and the integument; inner surface with the auricular cartilage.

Action.--Flexes the scapha mediad on the concha, thus enlarging the external opening of the concha.

=M. auricularis externus= (Fig. 169, 10; Fig. 64, r).--This consists of small scattered bands of interrupted fibres on the convex surface of the auricle, caudad of the transversus auriculæ. The largest of these bands runs parallel with the transversus auriculæ about five or six millimeters caudad of the latter. It has origin on the eminentia conchæ distad of the insertion of the abductor auris longus. Thence the fibres run distad five or six millimeters and are interrupted by an attachment to the cartilage. Distad the fibres begin again, and the muscle runs thence distad for about one centimeter, the distal end being attached to the cartilage.

Caudad of this, especially of its proximal portion, are one or two small bands of fibres usually running parallel with it, but unconnected with it and with each other. The extent and distribution of these bands varies, and the direction of fibres is also variable.

Relations.--Outer surface with the integument; inner surface with the auricular cartilage.

Action.--Flexes the auricular cartilage.

=M. helicis= (Fig. 169, 3; Fig. 64, m).--A muscle about two centimeters in length and five or six millimeters in width, on the inner surface of the ear, along its cranial margin.

Origin on the medial surface of the concha, just caudad of the proximal end of the tragus. The fibres pass distad to be inserted on the auricular cartilage at the caudal angle of the notch which lies beneath the cranial edge of the auricle, along with the caudal fibres of the adductor auris superior (1).

Relations.--Lateral surface with the integument; medial surface with the tragus.

Action.--Draws proximad the cranial margin of the auricle.