AURICULAR MUSCLES 337 



muscles and the intervening aponeurosis lie between two layers of fascia, the 

 external of which is fused to the skin, while the internal moves freely over the 

 periosteum, to which it is loosely attached. Haemorrhages and abscesses 

 spread freely between the deep layer of fascia and the periosteum. 



The frontalis is a large, thin muscle with convex upper and concave lower border. It arises 

 from the epicranial aponeurosis midwaj^ between the coronal suture and the orbital arch, and is 

 inserted into the skin of the eyebrow and of the root of the nose. The medial fibre-bundles take 

 a sagittal direction; the lateral converge obliquely toward the brow. The medial margins of 

 the muscles of each side are approximated near the attachment. The more medial fibre-bundles 

 are continuous with those of the procerus (pyramidahs nasi) and the angular portion (levator 

 labii superioris alseque nasi) of the quadratus labii superioris; the more lateral interlace with those 

 of the corrugator and orbicularis muscles. The branches of the vessels and nerves of the frontal 

 region pierce the muscle and are distributed between it and the skin. 



The occipitalis, flat and quadrangular, lies on the occipital bone above the supreme nuchal 

 line. It rises by tendinous fibres from the lateral two-thirds of this line and from the posterior 

 part of the mastoid process of the temporal bone, and is inserted into the epicranial aponeurosis. 

 The medial fibre-bundles run sagitaUy, while the lateral run obliquely forward. The occipital 

 artery and nerve lie between the muscle and the skin. The lateral border of the muscle comes 

 in contact with the posterior auricular muscle. The muscles of each side are usually separated 

 by a strip of aponeurosis. 



The galea aponeurotica (epicranial aponeurosis) is a fibrous membrane which extends be- 

 tween the occipital muscles and from them anteriorly to the frontal muscles. In the area be- 

 tween these two sets of muscles it is composed largely of sagitaUy running fibres into which 

 coronal fibres radiate from the region of the muscles of the ear. Between the two occipital 

 muscles the aponeurosis is attached_Jq_the suprem^^nuchal hne and external occipital protub^frrl^ 

 ance. Laterally the fascia covering it is continued as a special investment of the auricular 

 muscles, beyond which it is attached to the mastoid process, the zygoma, and to the external 

 cervical and the masseteric fasciae. 



Nerve-supply. — -The frontalis is suppUed by the temporal branches of the facial nerve, the 

 occipitalis by the posterior auricular branch. The branches enter the deep surface of each of 

 these muscles near its lateral border. 



Action. — The occipitahs serves to draw back and to fix and make tense the epicranial ap- 

 oneurosis. The frontalis, with its aponeurotic extremity fixed, elevates the brows and throws I 

 the skin of the forehead into transverse wrinkles as in the expression of attention, surprise, or ^ / 

 horror. When both muscles contract forcibly there is, in addition, a tendency to make the ^ 

 hair stand on end because the hair-bulbs of the occipital region slant forward, those of the frontal 

 region backward. The frontalis when fixed below puUs the scalp forward. 



Variations. — The occipitalis is occasionally absent, a condition normal in ruminants. The 

 muscles of the two sides may be fused in the median line (normal in dogs). It may be fused 

 with the posterior auricular. The frontahs is rarely missing. The frontalis may send slips 

 to the medial or lateral angles or the orbital arch of the frontal bone, to the nasal process of the 

 maxilla or to the nasal bone. The fibre-bundles of the frontalis may interdigitate across the 

 median line. 



The transversus nuchas, or occipitahs minor, is a small muscle, frequentlj- present (27 per 

 cent., Le Double), which runs from the occipital protuberance toward the posterior auricular 

 muscle, with which it may be fused. It may lie over or under the trapezius. 



(g) AURICULAR MUSCLES 

 (Fig. 341) 



The intrinsic muscles of the auricle are described in Section VIIL There are 

 three 'extrinsic' auricular muscles which converge from regions anterior, superior, 

 and posterior to the auricle and are inserted into it. 



The auricularis anterior (attrahens aurem) is a small, flat, triangular muscle which arises 

 between the two layers of the fascia of the galea aponeurotica, extends over the zj'gomatic arch, 

 and is attached to the ventral end of the helix. The fibre-bundles converge from the origin 

 toward a tendon of insertion. The area of origin of this muscle is often marked b}' a fibrous 

 band tangential to its component fibres. From this band muscle fibre-bundles radiate out 

 toward the frontal region of the skull. To the muscle formed of these radiating fibres the names 

 epicranio -temporalis (Henle), temporalis superficialis (Sappey) and auriculo-frontalis (Gegen- 

 baur) have been given. 



The auricularis superior (attoUens .-^.urem) is a large, thin, triangvirar muscle which, from 

 its tendinous insertion on the eminence of the triangular fossa of the ear, radiates upward into 

 the fascia of the galea aponeurotica, between the layers of which it takes oigin near the temporal 

 ridge. It hes over the temporal fascia and the periosteum of the parietal bone. 



The auricularis posterior (retrahens aurem) is a thin, band-like muscle which extends over 

 the insertion of the sterno-cleido-mastoid from the base of the mastoid process and the ap- 

 oneurosis of the sterno-cleido-mastoid muscle to the convexity of the concha, where it has a ten- 

 dinous insertion. It is usually composed of two fasciculi, and is contained between two layers 

 of fascia derived from the galea aponeurotica. 



Nerve-supply. — The auricularis anterior and superior are supphed by the temporal branch 

 of the facial, the auricularis superior and posterior by the posterior auricular branch. The 

 twigs of supply run to the deep surface of the muscles. 

 22 



