428 THE MUSCLES 



Insertion. — The posterior border of the epicranial aponeurosis, about one inch 

 and a half (3 '7 cm.) above the su})erior nuchal line of the occipital bone. 



(2) The frontalis — a curved sheet of somewhat quadrilateral shape, Avith a 

 convex upper, and a concave lower border. 



Origin. — The ei)irranial aponeurosis, aljout half-way between the coronal 

 suture and the orbital arch. 



Insertion. — The deep surface of the skin of the eyebrow and of that which 

 occupies the space at the r(^ot of the nose between the eyebrow and the middle 

 line. 



(3) The epicranial aponeurosis forms the central tendon of the occipito- 

 frontalis, and its attachments will be described with the structure of the muscle. 



Structure. — The occipitalis is thin and pale, and arises by sliort tendinous inter- 

 mingled with muscular fibres, and, after passing in parallel lines for about one inch 

 and a half (3' 7 cm. ) upwards, it is inserted into the epicranial aponeurosis, a strong 

 curved sheet, which occupies the whole of the surface of the skull from the superior 

 nuchal lines l^ehind to the eyebrows in front, and is continued laterally over the 

 temporal fascia of either side to about the level of the external auditory meatus. 

 Al)ove, it is tendinous, and composed of fibres which run from behind forwards. 

 It is thin in front and behind, where it forms a sort of sheath to the occipitalis and 

 frontalis muscles; but near the median line behind, it is thick where it fills up the 

 interval between the occipitales. Laterally, it becomes very thin, and is lost in 

 the loose connective tissue superficial to the temporal fascia after having given 

 origin to the attrahens and attollens aurem muscles. In front, a narrow triangular 

 slip, with the base upwards and the apex between the eyebrows, is left betAveen the 

 frontales, which are larger and somewhat thicker than the occipitales. The fibres 

 of the frontales run in parallel Inmdles downwards and slightly inwards, and are 

 lost in the subcutaneous fat of the eyebrows; while near the middle line a small 

 slip is continued upon the bridge of the nose as the pyramidalis, after entering 

 into close relation with the deep surface of the skin at the junction of the forehead 

 and nose. 



Nerve-supply. — The occipitalis receives one of the divisions of the posterioi 

 auricular branch from the facial or seventh cranial nerve. Its filaments enter the 

 deep surface of the muscle close to the outer border. 



The frontalis is supplied by the temporal branch of the temporo-facial divi- 

 sion of the facial nerve which is distriljuted to the deep surface near its outer 

 border. 



Action. — The occipitales draw back the epicranial aponeurosis, and with it the 

 scalp, which is intimately attached to its superficial aspect. Acting from behind, 

 the frontales raise the eyebrows. If these are fixed by the contraction of the 

 orbicularis palpebrarum, the frontalis will draw forwards the epicranial aponeu- 

 rosis and scalp. When both occipitales and frontales contract, they raise the 

 eyebrows to the utmost extent, and throw the skin of the forehead into transverse 

 "wrinkles, as in the expression of surj^rise or horror. At the same time, on account 

 of the direction of the hair-bulbs, which lie with a forward slant behind and a 

 backward slant in front, there will be a tendency to lift the hair shafts, and to 

 make them ' stand on end, like quills upon the fretful porcupine.' 



When the frontalis alone contracts, taking its fixed point from above, a slight 

 elevation of the eyebrow is produced, as in the expression of attention. This is 

 also accompanied by a transverse wrinkling of the forehead. 



Relations. — Superficially, the epicranial aponeurosis and its muscles are in 

 very close connection with the skin of the scalp and forehead, being only separated 

 from it by granular fat which is contained in small com]iartments formed b}' fibrous 

 septa extending from the aponeurosis to the deep surface of the skin. In tlie fat 

 lie the hair-bulbs and blood-vessels of the scalp. Beneath, it is separated from the 

 pericranium and temporal fascia by very loose connective tissue. 



Variations.-— The occipitalis may be continuous with the retrahetis aurem. The frontalis may 

 have insertions into the external or internal angle of the frontal bone, the nasal process of the 

 maxilla, or the uasal bone. 



