174 LEVA TOR LABII SUPERIORIS. 



palpebrarum muscle, the facial artery, and the integument. By its 

 deep surface with the superior maxillary bone, compressor nasi, alar 

 cartilage, and with a muscular fasciculus attached only to the bone, 

 and thence called musculus anomalus. 



The LEVATOR LABII SUPERIORIS PROPRIUS is a thin quadrilateral 

 muscle : it arises from the lower border of the orbit, and passing ob- 

 liquely downwards and inwards, is inserted into the integument of the 

 upper lip ; its deep fibres being blended with those of the orbicularis. 



Relations. By its superficial surface with the lower segment of the 

 orbicularis palpebrarum, with the facial artery, and with the integu- 

 ment. By its deep surface with the origins of the compressor nasi and 

 levator anguli oris muscle, and with the infra-orbital artery and nerve. 



The LEVATOR ANGULI ORIS arises from the canine fossa of the 

 superior maxillary bone, and passes outwards to be inserted into the 

 angle of the mouth, intermingling its fibres with those of the orbicu- 

 laris, zygomatici, and depressor anguli oris. 



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

 rioris proprius, the branches of the infra-orbital artery and nerve, and 

 inferiorly with the integument. By its deep surface with the superior 

 maxillary bone and buccinator muscle. 



The ZYGOMATIC muscles are two slender fasciculi of fibres which 

 arise from the malar bone, and are inserted into the angle of the mouth, 

 where they are continuous with the other muscles attached to this 

 part. The zygomaticus minor is situated in front of the major, and is 

 continuous at its insertion with the levator labii superioris proprius ; 

 it is not ^infrequently wanting. 



Relations. The zygomaticus major muscle is in relation by its super- 

 ficial surface with the lower segment of the orbicularis palpebrarum 

 above, and the fat of the cheek and integument for the rest of its ex- 

 tent. By its deep surface with the malar bone, the masseter, and buc- 

 cinator muscle, and the facial vessels. The zygomaticus minor being 

 in front of the major, has no relation witli the masseter muscle, while 

 inferiorly it rests upon the levator anguli oris. 



The DEPRESSOR LABII SUPERIORIS AL^EQUE NASI (myrtiformis) 

 is seen by drawing upwards the upper lip, and raising the mucous 

 membrane. It is a small oval slip of muscle, situated on each side of 

 the fraenum, arising from the incisive fossa, and passing upwards to be 

 inserted into the upper lip and into the ala and columna of the nose. 

 This muscle is continuous by its outer border with the edge of the 

 compressor nasi. 



Relations. By its superficial surface with the mucous membrane of 

 the mouth, the orbicularis oris and levator labii superioris alaeque nasi 

 muscle ; and by its deep surface with the superior maxillary bone. 



Actions. The orbicularis oris produces the direct closure of the lips 

 by means of its continuity at the angles of the mouth, with the fibres 

 of the buccinator. When acting singly in the forcible closure of the 

 mouth, the integument is thrown into wrinkles in consequence of its 

 firm connection with the surface of the muscle. The levator labii 



