276 THE MUSCLES. 



distance from the commissure of the lips. Covered by the skin, it covers the 

 buccinator, and some of the superior molar glands, vessels, and nerves. 



When this muscle contracts, it pulls back the commissure of the lips. 



In SoJipeds there is also sometimes found a muscle resembling the zygomaticus 

 ininoi' of Man. It is a very small fasciculus situated under the preceding muscle, 

 near its superior extremity. It appears that this fasciculus is continued, above, 

 by the fibres of the lachrymal muscle, and is lost, below, on the buccinator sur- 

 face, a little beneath the carotid canal. 



3. SUPERMAXILLO-LABIALIS (LEVATOR LaBII SuPERIORIS PrOPRIUS, OR NaSALIS 



LONGUS) (Fig. 168, 16). 



Synonyms. — Levator labii superioris of Bourgelat. The levator labii superioris proprii of 

 Man. {Nasalis longus labii superioris — Percivall.) 



Situation — Direction— Form — Structure. — Lying vertically on the side of the 

 face, below the levator labii superioris alseque nasi, this muscle is a thick and 

 conical fleshy mass, terminated inferiorly by a tendon. 



Attachments. — It is attached, by the upper extremity of its fleshy body, to the 

 external surface of the supermaxillary and zygomatic bones — origin. Its terminal 

 tendon passes over the transverse muscle of the nose, to unite with that of the 

 opposite side, and with it to form a single aponeurotic expansion, which dips by 

 small fibres into the subcutaneous musculo-fibrous tissue of the upper lip. 



Relations. — Covered by the lachrymal and levator superioris alfequi muscles, 

 this muscle in turn covers the supermaxiUary bone, the bottom of the false nostril, 

 the dilatator naris inferioris, and the transversalis nasi. 



Actions. — It raises the upper lip, either directly or to one side, as it acts singly 

 or in concert with its congener on the opposite side. 



4. Maxillo-labialis (Depressor Labii Inferioris) (Fig. 168, 28). 



Synonyms. — Depressor labii inferioris — Bigot. A dependency of the buccinator of Man. 

 (Depressor labii inferioris — Percivall. Inferior maxillo-labialis — Leyh. Depressor anguli oris 

 of Man.) 



Situation — Direction — Form — Structure. — Situated along the inferior border 

 of the buccinator, and following its direction, this muscle forms a long narrow 

 fasciculus, terminating inferiorly by an expanded tendon. 



Attachments. — 1. By its superior extremity, to the anterior border of the 

 lower jaw, in common with the deep plane of the buccinator— ^a;^c? origin. 2. 

 By its terminal tendon, to the skin of the lower lip — movat)le insertion. 



Relations. — Outwardly, with the masseter and the facial portion of the cervical 

 panniculus ; inwardly, with the maxillary bone ; in front, with the buccinator, 

 with which it is directly united in its upper two-thirds. 



Actions. — It separates the lower from the upper lip, and pulls it to the side 

 if one alone acts. 



5. Mento-labialis, or Muscle of the Chin (Levator Menti) (Fig. 168, 29). 



[Synonyms. — Percivall appears to describe this and the next muscle as one, the levator menti. 

 It is the quadratus menti of Man.) 



This name is given to a musculo-fibrous nucleus, forming the base of the 

 rounded protuberance beneath the lower hp in front of the beard. This single 

 nucleus is confounded, in front, with the orbicularis of the lips, and receives into 

 its upper face the insertion of the two posterior middle muscles (levatores menti). 



