380 MYOLOGY 



The medial margins of the Frontales are joined together for some distance above 

 the root of the nose; but between the Occipitales there is a considerable, though 

 variable, interval, occupied by the galea aponeurotica. 



The galea aponeurotica (epicranial aponeurosis) covers the upper part of the 

 cranium; behind, it is attached, in the interval between its union with the Occipi- 

 tales, to the external occipital protuberance and highest nuchal lines of the occipital 

 bone; in front, it forms a short and narrow prolongation between its union with 

 the Frontales. On either side it gives origin to the Auriculares anterior and supe- 

 rior; in this situation it loses its aponeurotic character, and is continued over the 

 temporal fascia to the zygomatic arch as a layer of laminated areolar tissue. It 

 is closely connected to the integument by the firm, dense, fibre-fatty layer which 

 forms the superficial fascia of the scalp : it is attached to the pericranium by loose 

 cellular tissue, which allows the aponeurosis, carrying with it the integument to 

 move through a considerable distance. 



Variations. Both Frontalis and Occipitalis vary considerably in size and in extent of attach- 

 ment; either may be absent; fusion of Frontalis to skin has been noted. 



Nerves. The Frontalis is supplied by the temporal branches of the facial nerve, and the 

 Occipitalis by the posterior auricular branch of the same nerve. 



Actions. The Frontales raise the eyebrows and the skin over the root of the nose, and at the 

 same time draw the scalp forward, throwing the integument of the forehead into transverse 

 wrinkles. The Occipitales draw the scalp backward. By bringing alternately into action the 

 Frontales and Occipitales the entire scalp may be moved forward and backward. In the ordinary 

 action of the muscles, the eyebrows are elevated, and at the same time the aponeurosis is fixed 

 by the Occipitales, thus giving to the face the expression of surprise; if the action be exaggerated, 

 the eyebrows are still further raised, and the skin of the forehead thrown into transverse wrinkles, 

 as in the expression of fright or horror. 



A thin muscular slip, the Transversus nuchse, is present in a considerable pro- 

 portion (25 per cent.) of cases; it arises from the external occipital protuberance 

 or from the superior nuchal line, either superficial or deep to the Trapezius; it 

 is frequently inserted with the Auricularis posterior, but may join the posterior 

 edge of the Sternocleidomastoideus. 



H. THE MUSCLES OF THE EYELIDS. 

 The muscles of the eyelids are : 



Levator palpebrse superioris. Orbicularis oculi. Corrugator. 



The Levator palpebra? superioris is described with the Anatomy of the Eye. 



The Orbicularis oculi (Orbicularis palpebrarum) (Fig. 379) arises from the nasal 

 part of the frontal bone, from the frontal process of the maxilla in front of the 

 lacrimal groove, and from the anterior surface and borders of a short fibrous band, 

 the medial palpebral ligament. From this origin, the fibers are directed lateral- 

 ward, forming a broad and thin layer, which occupies the eyelids or palpebrse, 

 surrounds the circumference of the orbit, and spreads over the temple, and down- 

 ward on the cheek. The palpebral portion of the muscle is thin and pale ; it arises 

 from the bifurcation of the medial palpebral ligament, forms a series of concentric 

 curves, and is inserted into the lateral palpebral raphe. The orbital portion is thicker 

 and of a reddish color; its fibers form a complete ellipse without interruption at 

 the lateral palpebral commissure; the upper fibers of this portion blend with the 

 Frontalis and Corrugator. The lacrimal part ( Tensor tarsi) is a small, thin muscle, 

 about 6 mm. in breadth and 12 mm. in length, situated behind the medial palpebral 

 ligament and lacrimal sac (Fig. 379). It arises from the posterior crest and adjacent 

 part of the orbital surface of the lacrimal bone, and passing behind the lacrimal 

 sac, divides into two slips, upper and lower, which are inserted into the superior 

 and inferior tarsi medial to the puncta lacrimalia; occasionally it is very indistinct. 



