MUSCLES OF THE HEAD 433 



of the nose the tendons, the one on the right side and the other on the left, 

 blend together and unite in one common tendon, which is inserted upon 

 the superior part of the uj^per lip. Action — to corrugate the upper lip, and 

 thence to raise it. 



Caninus is situated over the two anterior molar teeth. Origin — from the 

 superior maxillary bone, near its junction with the anterior maxilla. Insertion 

 — to a roughened depression on the inferior maxillary bone, just behind the 

 lower tush. Action — to assist in closing the mouth. 



Dilatator naris anterior is situated in front of and between the nostrils. 

 Origin — from the supei'O-anterior surface of the os nasi. Insertion — to the 

 anterior part of the alar cartilages, blending with the orbicularis oris. 

 Action — to I'aise the uj^per lip. 



Nasalis brevis labii superioris is situated behind the nostrils. Origin 

 — from the superior and anterior maxillary bones, and from the suture 

 uniting them. Insertion — to the supero-anterior part of the septum nasi, 

 and to the skin of the false nostrils. Action — to dilate the nostrils. 



Buccinator is situated between the upper and lower jaws. Origin — 

 from the tuberosity of the superior maxillaiy bone, and from the outer walls 

 of the alveolar cavities of the upper molar teeth. Insertion — to the outer 

 walls of the alveolar cavities of the lower molar teeth. In front it is 

 blended with the orbicularis oris. Action — to draw back the angle of the 

 lips, and tighten the outer wall of the mouth. 



Retractor labii inferioris is situated on the anterior part of the lower 

 jaw. Origin — from the extemial part of the lower jaw, just behind the last 

 molar tooth. Insertion — to the inferior part of the lower lip. This muscle 

 blends with the orbicularis oris. Action — to retract the lower lip. 



Naso transversalis is situated between the two alar cartilages. This 

 muscle runs between the antero-internal borders of each cartilage to which 

 it is attached, and its action tends to approximate them. 



Depressor labii superioris lies upon the anterior part of the upper jaw. 

 Origin — from the anterior maxillary bone, and from the outer border of the 

 alveoli of the incisor teeth, extending as far back as the tush. Insertion — 

 to the upper lip and inferior nasal cartilages. Action — to assist in dilating 

 the nostrils, and in retracting the upj)er lip. 



Orbicularis oris. — This sphincter muscle is situated within the border 

 of the lips. Origin — from the outer surfaces of the superior and inferior 

 maxillary bones. Insertion — it interlaces with its own fibres at the angles, 

 and is also attached to the glandular substance and skin of the lips. Action 

 — to contract the opening of the lips, and compress them against the jaws. 



Depressor labii inferioris lies along the side of the lower jaw. Origin 

 — from the side of the lower jaw, close to that of the buccinator. Insertion — 

 into the fat of the prominence of the chin. 



Levator menti is a little square muscle bracing the soft parts, covering 

 the chin, up against the jaw. It aiuses from the edge of the alveolar process 

 of the corner tooth on one; side, passes beneath the chin, and meets there its 

 fellow of the opposite side. 



