The Scutiform Cartilage.—Closely connected with the external ear, but not forming a part of it, is the scutiform cartilage. This lies in the temporal fossa, between the integument and the temporal muscle, just behind the orbit and beneath the craniomedial portion of the auricle ([Fig. 63], 1, [page 97]). It is a narrow cartilage about two centimeters long, with its long axis craniocaudal. For the greater part of its length it forms a slender rod, from which a thin cartilaginous sheet extends a short distance laterad; at its caudal end the rod forks, the two arms extending nearly at right angles to the main portion. The scutiform cartilage serves for the origin or insertion of a number of the muscles of the ear.
Muscles of the External Ear ([Fig. 169]).—(a) The muscles connecting the cartilages of the external ear with other parts of the head have been described ([page 96]), excepting the tragicus lateralis (4). These muscles are the following: M. intermedius scutulorum ([Fig. 63], a), M. frontoauricularis, M. levator auris longus (including the cervicoauricular) ([Fig. 63], g, g′), M. auricularis superior ([Fig. 63], k), M. abductor auris longus ([Fig. 63], m), M. abductor auris brevis ([Fig. 63], l), M. zygomaticus ([Fig. 64], d), M. submentalis ([Fig. 64], c), M. depressor conchæ ([Fig. 64], b), M. frontoscutularis, M. adductor auris inferior ([Fig. 63], f), and M. tragicus lateralis ([Fig. 169], 4).
M. tragicus lateralis ([Fig. 169], 4).—A band about seven millimeters wide, lying beneath the mass of fat about the ear and running ventrad lengthwise of the concha and close against it.
Origin ([Fig. 96], a, [page 229]) on the caudal end of the mandibula, in the cavity found between the condyloid process and the angular process. The muscle passes dorsad and is inserted ([Fig. 169], 4) on the caudal margin of the tragus and in the depression on the concha just caudad of the tragus.
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.