MUSCLES OF THE LIPS AND MOUTH. 271 



the angle of the mouth and that of the lower lip ; and lastly, acting 

 indirectly on the lower lip, the levator menti. 



The orbicularis oris muscle, or sphincter oris, consists of labial and 

 facial parts. The Jahkil or marginal part occupies the red part of the lips, 

 and forms a slightly convex fasciculus of pale fine fibres which are free 

 fi'om bony attachment, and can be traced from one lip to another round 

 the corner of the mouth. Ihe facial part, thinner and wider than the 

 other, blends by its outer border with the several contiguous muscles 

 that converge to the mouth, and more particularly with the buccinator 

 muscle, the fibres of which are continuous with the deeper part of the 

 orbicularis. Besides those fibres it has others, musciiU incisivi (Henle), 

 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 the outer slip, thin and weak, passes down- 

 wards, and is attached opposite the incisor teeth, close to the alveolar 

 edge of the upper jaw-bone ; while the other, thick and pointed, passes 

 npvN'ards and is fixed to the septum of the nose. In the lower lip the 

 reinforcing fasciculus arises from the surface of the lower jaw, near 

 the root of the canine tooth, and external to the levator labii mferioris, 

 and passing directly outwards towards the angle of the mouth, its fibres 

 blend w4th the rest of the muscle. 



delations. — The skiii of the lips is closely connected to the inner jiart of the 

 orbiculaiis oris muscle, whilst over the outer part fatty tissue is interi^osed 

 between them. The deep surface is in contact with the mucous membrane and 

 the labial glands, as well as with the coronaiy arteiial arch in each lip. 



The levator labii superioris proprius muscle arises from the 

 superior maxillary bone immediately above the infraorbital foramen, 

 and from the adjoining surface of the malar bone ; it passes downwards 

 and a little inwards to be blended with the orbicularis and other mus- 

 cular fibres in the upper lip. 



Belat'wns. — At its origin this muscle is overlapped by the orbicularis palpe- 

 brarum, but its lower part is subcutaneous ; it partly- conceals the levator ang-uli 

 oris and the compressor naris, and beneath it the infraorbital vessels and nerve 

 emerge from the canal of that name. 



Varictka. — This muscle is frequently united with the levator lab. sup. alasque 

 nasi. It is also commonly seen arising by t^^'O heads, the outer being attached to 

 the malar bone, or coming as a slip from the orbicularis palpebrarum. 



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

 canine fossa immediately below the infraorbital foramen, inclines down- 

 wards and slightly outwards, and is inserted into the angle of the 

 mouth, where it becomes blended with the fibres of the orbicularis, 

 zygomatici and depressor anguli oris. 



liclations. — At its origin this muscle is concealed by the proper elevator of the 

 upper lii> ; its anterior surface supports the infraorbital nerve and artery, which 

 separate ib from the preceding muscle ; the posterior surface lies on the superior 

 maxillii and the orbicularis and buccinator muscles, with which and the depressor 

 anguli oris the fibres are blended. 



The ZYGOMATICI are two narrow and subcutaneous fasciculi of mus- 

 cular fibres, extending obliquely from the most prominent part of the 

 cheek to the angle of the mouth, one being thicker and longer than the 

 other. 



