SUPERIOR LABIAL GROUP. 173 



The DILATATOR NARIS is a thin and indistinct muscular apparatus 

 expanded upon the ala of the nostril, and consisting of an anterior and 

 a posterior slip. The anterior slip (levator proprius alae nasi anterior) 

 extends between the lateral and alar cartilage at about midway be- 

 tween the tip and the attached margin of the nose. The posterior 

 slip (levator proprius alse nasi posterior) is attached above to the 

 margin of the nasal process of the superior maxillary bone, and below 

 to the small cartilages of the ala nasi. These muscles are difficult of 

 dissection from the close adherence of the integument to the nasal car- 

 tilages, 



Actions. The pyramidalis nasi, as a point of attachment of the 

 occipito-frontalis, assists that muscle in its action : it also draws down 

 the inner angle of the eyebrow, and by its insertion fixes the aponeu- 

 rosis of the compressores nasi. The compressores nasi appear to act in 

 expanding rather than in compressing the nares ; hence probably the 

 compressed state of the nares from paralysis of these muscles in the 

 hast moments of life, or in compression of the brain. The use of the 

 dilatator naris is expressed in its name. 



5. Superior Labial Group. Orbicularis oris, 



Levator labii superioris alaeque nasi, 



Levator labii superioris proprius, 



Levator anguli oris, 



Zygomaticus major, 



Zygomaticus minor, 



Depressor labii superioris alaeque nasi. 



The ORBICULARIS ORIS is a sphincter muscle, completely surround- 

 ing the mouth, and possessing -consequently neither origin nor inser- 

 tion. It is composed of two thick semicircular planes of fibres, which 

 embrace the rima of the mouth, and interlace at their extremities, 

 where they are continuous with the fibres of the buccinator, and of 

 the other muscles connected with the angle of the mouth. The upper 

 segment is attached by means of a small muscular fasciculus (naso- 

 labialis) to the columna of the nose ; and other fasciculi connected 

 with both segments and attached to the maxillary bones are termed 

 "accessorii." 



Relations. By its superficial surface with the integument of the 

 lips with which it is closely connected. By its deep surface with the 

 mucous membrane of the mouth, the labial glands and coronary arteries 

 being interposed. By its circumference with the numerous muscles 

 which move the lips, and by the inner border with the mucous mem- 

 brane of the rima of the mouth. 



The LEVATOR LABII SUPERIORIS AL^QUE NASI is a thin trian- 

 gular muscle ; it arises from the upper part of the nasal process of the 

 superior maxillary bone ; and, becoming broader as it descends, is in- 

 serted by two distinct portions into the ala of the nose and upper lip. 



Relations. By its superficial surface with a part of the orbicularis 



