SUPERIOR LABIAL GROUP. 151 



border corresponds with the edge of the orbicularis palpebrarum, 

 and its inner border with its fellow, from which it is separated by 

 a slight interval. 



The compressor nasi is a thin and triangular muscle; it arises by 

 its apex from the canine fossa of the superior maxillary bone, and 

 spreads out upon the side of the nose into a thin tendinous expan- 

 sion, which is continuous across its ridge with the muscle of the 

 opposite side. 



Relations. By its superficial surface with the levator labii supe- 

 rioris proprius, the levator labii superioris alaeque nasi, and the inte- 

 gument ; by its deep surface with the superior maxillary and nasal 

 bone, and with the alar and lateral cartilages of the nose. 



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 

 aponeurosis of the comprcssores 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 last moments of life, or in compression of the 

 brain. 



5. Superior Labial Group. Orbicularis oris, 



Levator labii superioris alceque nasi, 

 Levator labii superioris proprius,* 

 Levator anguli oris, 

 Zygomaticus major, 

 Zy'gomaticus minor, 

 Depressor labii superioris aloeque nasi. 



The orbicularis oris is a sphincter muscle, completely surrounding 

 the mouth, and possessing consequently neither origin nor insertion. 

 It is composed of two thick semicircular planes of fibres, which em- 

 brace 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. 



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 membrane of the rima of the mouth. 



The levator labii superioris alcegue nasi is a thin triangular muscle; 

 it arises from the nasal process of the superior maxillary bone; and, 

 becoming broader as it descends, is inserted by two distinct por- 

 tions into the integument of the ala of the nose and upper lip. 



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



* These two levators are described as one by Homer. G. 



