THE ORBICULARIS ORIS. 557 



and are continued across from side to side. Those of the elevator levatorand 

 and depressor muscles, having crossed at the corner of the mouth, anguiforis, 

 turn inwards in the opposite lip, in front of the buccinator fibres, 

 and are inserted into the skin, for the most part crossing the middle 

 line and decussating with the fibres entering on the other side. A 

 compact superficial fasciculus at the red margin of the lip is formed 

 solely by buccinator fibres. In the upper lip there are also two 

 slips arising, the one (naso-laUal, fig. 202) from the hinder part of naso-labial 

 the septum narium, the other (incisive) from the outer part of the and incisive 

 incisor fossa of the superior maxilla, and directed outwards to the sllps- 

 corner of the mouth ; while in the lower lip there is a similar 

 incisive slip attached to the incisor fossa of the inferior maxilla. To 

 see these attachments, the lip must be everted and the mucous 

 membrane carefully raised. 



Towards the free margin in each lip there are fibres directed ob- Special 

 liquely from the skin to the mucous membrane, between the fasciculi fjplj 68 ( 

 of the orbicularis : they constitute the muse, labii proprius. 



The inner margin of the orbicularis is free, and bounds the Relation of 

 aperture of the mouth ; the outer edge blends with the different r 

 muscles that elevate or depress the lips and the angle of the mouth. 

 Between the orbicularis and the mucous membrane in each lip are 

 the coronary artery and the labial glands. 



Art ion. The buccal portion of the muscle flattens the lips and use. 

 against the teeth, turns inwards the red margin, and gives a linear 

 form to the aperture. The superficial portion, derived from the 

 muscles of the angle of the mouth, brings the lips together both 

 vertically and horizontally, so as to diminish the size of the opening, 

 and causes the free edges of the lips to protrude. 



The LEVATOR MESTI (levator labii inferioris) is a small muscle Elevator of 

 on the side of the fraenum of the lower lip, which is opposite the cnin: 

 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 the iucissor fossa 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, use. 

 and assists in raising the lower lip. 



The principal VESSELS OF THE FACE (fig. 204) are the facial and Arteries of 

 transverse facial arteries with their accompanying veins. The 

 arteries are branches of the external carotid ; and the facial vein is 

 received into the internal jugular trunk. 



The FACIAL ARTERY (fig. 204, #), a branch of the carotid, Facial 

 emerges from the neck, and crosses the base of the lower jaw a ry " 

 immediately in front of the masseter muscle. From this point the 

 artery ascends in a tortuous manner, near the angle of the mouth 

 and the side of the nose, to the inner margin of the orbit, where it 

 anastomoses with the terminal branches of the ophthalmic artery, course 

 The course of the vessel is comparatively superficial in the mass of 

 fat of the inner part of the cheek. At first it is concealed by the 



