EPICRANIAL MUSCLES. 169 



of insertion are often continued into aponeuroses of investment, as in the 

 instance of the glutens maximus, or into mere fascia, as at the lateral parts 

 of the occipito-frontal aponeuroses, or the cranial origin of the trapezius 

 muscle. The principal aponeuroses of investment are those which incase 

 the muscles of the limbs, binding them down in a common sheath, and 

 connected in various places by septa with the bones. They are characteristic 

 of the limbs, there being no structure entirely C3rresponding to them in 

 the rest of the body. 



MUSCLES OF THE HEAD AND NECK. 



SUPERFICIAL MUSCLES. 



EPICRANIAL MUSCLES. Under the title of occipito-frontalis muscle are 

 comprehended a pair of occipital and a pair of frontal muscles, together 

 with a thin aponeurosis extending over the cranium, and uniting the 

 anterior and posterior muscles together. 



a. The occi2ntalis muscle, thin and subcutaneous, is attached inferiorly 

 by short tendinous fibres to the external two-thirds, sometimes much less, 

 of the superior curved line of the occipital bone, and to the mastotd portion 

 of the temporal bone, immediately above the attachment of the sterno- 

 mastoid muscle. Its fleshy fibres, from one to two inches in length, are 

 directed upwards, and terminate in distinct tendinous fibres, continuous 

 with the epicranial aponeurosis. Between the muscles of opposite sides is 

 an interval of variable size occupied by a part of that aponeurosis. 



6. The frontalis muscle, longer and broader and of a paler colour than 

 the occipitalis, arises superiorly in a convex line from the epicranial 

 aponeurosis, while inferiorly its innermost fibres are continuous with the 

 pyramidalis nasi muscle, and the others are blended with the corrugator 

 supercilii and with the orbicularis palpebrarum, as far outwards as the 

 external orbital process of the frontal bone. The fibres are nearly vertical, 

 running slightly inwards ; the margins of the right and left muscles are 

 united for a short distance above the root of the nose, but are separated by 

 an angular interval superiorly. 



c. The epicranial or occipito-frontal aponeurosis extends over the upper 

 surface of the cranium uniformly from side to side, without division. Pos- 

 teriorly it is attached to the occipitales muscles, and to the protuberance 

 and superior curved lines of the occipital bone, and anteriorly it terminates 

 in the frontales muscles, while laterally it presents no distinct margin, but 

 below the temporal ridge becomes thinner and less aponeurotic, and gives 

 attachment to the superior and anterior auricular muscles. Its fibres are 

 chiefly longitudinal, and are most distinctly tendinous where they give 

 attachment to the occipitales muscles. Its outer surface is firmly bound to 

 the skin by an abundant network of fibrous tissue, constituting the so- 

 called superficial fascia, by the meshes of which the subcutaneous fat is 

 divided into granules ; while its deep surface glides upon the subjacent peri- 

 cranium, to which it is loosely adherent through the medium of a delicate 

 connective tissue devoid of fat. 



ACTIONS. By the contraction of the whole occipito-frontalis muscle, the scalp is 

 drawn backwards, and the eyebrows elevated ; by the contraction of the frontales 

 muscles alone, the eyebrows are elevated, the scalp pulled forwards, and the skin of 

 the forehead thrown into transverse wrinkles ; by the contraction of the occipitales 

 muscles alone, the scalp is drawn backwards ; and by the alternate action of the 

 occipitales and frontales muscles, the scalp is moved backwards and forwards. In 



