38 DISSECTION OF THE FACE. 



lower lip it is fixed on each side into the inferior jawbone, opposite the 

 canine tooth, external to the levator labii inferioris muscle. To see these 

 attachments the lip must be everted, and the mucous membrane carefully 

 raised. 



The inner margin of the muscle is free, and bounds the aperture of the 

 mouth ; whilst the outer edge blends with the ditferent muscles that ele- 

 vate or depress the lips and the angle of the mouth. Beneath the orbicu- 

 laris in each lip is the coronary artery, with the mucous membrane and 

 the labial glands. 



Action. Both parts of the muscle contracting, the lips are pressed to- 

 gether and projected forwards, and the aperture of the mouth is diminished 

 transversely by the approximation of the corners towards each other. 



The inner fibres acting alone will turn inwards the red part of the lip, 

 and diminish the width of the buccal opening. 



The outer fibres press the lips against the dental arches, the free edges 

 being protruded and somewhat everted. At the same time the centre part 

 of the nose is depressed and the chin raised by means of' the fleshy slips 

 connected with those parts. 



The LEVATOR LABII SUPERIORIS (fig. 6, 6 ) extends vertically from the 

 lower margin of the orbit to the orbicularis oris. It ;v'ses from the 

 upper maxillary and malar bones above the infra-orbital foramen, and 

 blends inferiorly with the orbicularis oris. Near the orbit the muscle is 

 overlapped by the orbicularis palpebrarum, but below that spot it is sub- 

 cutaneous. By its inner side it joins the common elevator of the ala of 

 the nose and upper lip ; and to its outer side lie the zygomatic muscles, the 

 small one joining it. Beneath it are the infra-orbital vessels and nerve. 



Action. By the action of this muscle the upper lip is raised, and the 

 skin of the cheek is bulged below the eye. 



The DEPRESSOR LABII INFERIORIS (fig. 6, 12 ) is opposite the elevator 

 of the upper lip, and has much yellow fat mixed with its fibres. The 

 muscle has a wide origin from a depression on the front of the lower jaw, 

 reaching backwards from near the symphysis to a little beyond the hole 

 for the labial vessels and nerve ; ascending thence it is united with the 

 orbicularis in the lower lip. Its inner border joins the muscle of the oppo- 

 site side above, and its outer is overlapped below by the depressor anguli 

 oris. 



Action. If one muscle contracts, the half of the lip of the same side is 

 depressed and everted ; but by the use of both muscles, the whole lip is 

 lowered and turned outwards, and rendered tense at the centre. 



The LEVATOR LABII INFERIORIS (levator menti) is a small muscle on 

 the side of the frsenum of the lower lip, which is opposite the depressor of 

 the ala of the nose in the upper lip. When the lip has been everted and 

 the mucous membrane removed, the muscle will be seen to arise from a 

 fossa near the symphysis of the lower jaw, and to descend to its insertion 

 into the integument of the chin. Its position is internal to the depressor 

 of the lip and the attachment of the orbicularis. 



Action. It indents the skin of the chin opposite its insertion, and 

 assists in raising the lower lip. 



The LEVATOR ANGULI ORIS (fig. 6, f) has well-marked fibres, and is 

 partly concealed by the levator labii superioris. Arising from the canine 

 fossa beneath the infra-orbital foramen, its fibres spread out towards the 

 angle of the mouth where they are superficial to the buccinator, and mix 



