THE HEAD, ANTERIOR. 63 



Insertion. Into the angle of the mouth, blending with 

 the other muscles at that point. 



Nerve Supply. The facial through its supramaxillary 

 branch. 



Action. To depress and retract the angle of the mouth. 



Depressor Labii Inferioris. 



Origin. From the upper border of the external oblique 

 line of the inferior maxilla, from near the symphysis to 

 beyond the mental foramen. 



Insertion. Into the orbicularis oris and the skin of the 

 lower lip. 



Nerve Supply. The supramaxillary branch of the facial. 



Action. To depress the lower lip. 



Levator Labii Inferioris. 



Origin. From the incisive fossa of the lower jaw. 

 Insertion. Into the skin of the chin. 

 Nerve Supply. The supramaxillary branch of the facial. 

 Action. To raise the skin over the point of the chin and 

 protrude the lower lip. 



Orbicularis Oris. Fig. 3. 



This is the sphincter muscle of the mouth, and is ar- 

 ranged in two portions, an internal or labial, and an exter- 

 nal or facial. 



The labial portion has no bony attachments. The facial 

 is attached by slender slips to the septum of the nose, and 

 the incisive fossae of the superior and inferior maxillary 

 bones, besides blending with the muscles passing to the 

 mouth. 



Nerve Supply. The facial through its buccal and supra- 

 maxillary branches. 



Action. To close the lips, vertically and transversely ; 



