MUSCLES OF THE LIPS AND MOUTH. 175 



and must aid it in drawing down the integument of the forehead ; but it probably 

 acts also as an opponent to the compressor naris muscle. The compressor naris, acting 

 along with its fellow of the other side, depresses the cartilaginous part of the nose, 

 and to some extent also compresses the alae together. The actions of the other 

 muscles are sufficiently indicated by their names ; the dilatation of the alae is per- 

 ceptible in natural inspiration, and is well marked in dyspnoea. 



MUSCLES OF THE LIPS AJSD MOUTH. Around the orifice of the mouth 

 are situated an orbicular muscle with concentric fibres, and numerous other 

 muscles, whose fibres converge towards the aperture, viz., superiorly the 

 common elevator of the lip and nose already described, the proper elevator 

 of the upper lip, the elevator of the angle of the mouth and the zygomatic 

 muscles, laterally the risorius and buccinator muscles, and, inferiorly, the 

 depressor of the angle of the mouth and that of the lower lip j and lastly, 

 acting indirectly on the lower lip, the levator menti. 



The orbicular is oris, or sphincter oris, consists of a labial or inner, and a 

 facial or peripheral part. The labial or marginal portion reaches outwards 

 from the oral aperture as far as the red part of the lip, and forms a slightly 

 convex fasciculus of pale fine fibres closely applied to each other. Its fibres 

 are free from bony attachment, and are traceable from one lip to another 

 round the corner of the mouth. The facial portion, thinner and wider than 

 the other, blends by its outer border with the several muscles that con- 

 verge to the mouth from the contiguous parts of the face, and is more 

 particularly stretched outwards by its attachment to the buccinator muscle, 

 the fibres of which seem almost to be continuous with the deeper part of 

 the orbicularis. Besides those fibres it has others that are attached to the 

 subjacent cartilage and bone ; viz., in the upper lip two bundles for each 

 half ; and in the lower lip one for each. In the upper lip one of the fleshy 

 slips (accessorius orbicularis superioris) is thin and weak, and is attached 

 opposite the incisor teeth, close to the alveolar edge of the upper jaw-bone ^ 

 and the other, thicker and pointed, is fixed to the septum of the nose. In 

 the lower lip the reinforcing fasciculus (accessorius orbicularis inferioris) 

 arises from the surface of the lower jaw, near the root of the canine tooth, 

 and external to the levator labii inferioris. From these points of attach- 

 ment the fibres are directed outwards towards the angle of the mouth and 

 blend with the rest. 



To the inner part of the orbicularis oris muscle the skin of the lips is closely con- 

 nected, whilst over the outer part fatty tissue is interposed between them. The deep 

 surface is in contact with the mucous membrane and the labial glands, as well as with 

 the coronary arterial arch in each lip. 



The levator labii superioris arises immediately above the infraorbital 

 foramen, close to the lower border of the crbit, from the superior maxillary 

 and malar bones, and passes downwards and a little inwards to be blended 

 with the orbicularis and other muscular fibres in the upper lip. 



At its origin this muscle is overlapped by the orbicularis palpebrarum, but its 

 lower part is subcutaneous ; it partly conceals the levator anguli oris, and the com- 

 pressor naris, and beneath it the infraorbital vessels and nerve emerge from the 

 canal of that name. 



The levator anguli oris, or musculus caninus, arises in the canine fossa 

 immediately below the infraorbital foramen, inclines downwards and slightly 

 outwards, and is inserted into the angle of the mouth. 



At its origin this muscle is concealed by the elevator of the upper lip ; its anterior 



