224 



FACE. 



connected with the thick skin which covers it. 

 The posterior surface and free border is covered 

 with the mucous membrane of the mouth, from 

 which it is only separated in places by the 

 labial glands, by the coronary vessels, arid by 

 numerous nerves. Its outer border or circum- 

 ference receives the antagonist muscles which 

 are attached around it. 



Actions. The orbicularis enjoys a very va- 

 ried and extensive motion, and possesses the 

 remarkable power of either acting as a whole 

 or in parts. Its simple use is to close the 

 mouth, in correspondence with the elevation 

 of the lower jaw, by bringing the red borders 

 of the lips in contact, or by pressing them to- 

 gether firmly. But the upper or lower labial 

 fibres can act separately, or the fibres at either 

 commissure, or the fibres of one side may con- 

 tract, while the others are quiescent, so that 

 different parts of the lips may be moved by 

 different portions of the muscle, which is made 

 in this way to antagonize in turn the different 

 muscles which are attached around. 



The lips may be thrown forward by the con- 

 traction of the labial and commissural fibres 

 forming in strong action a circular projection, 

 as in the action of whistling, or, when more 

 relaxed, in blowing. By the contraction of the 

 inner labial fibres the lips may, on the contrary, 

 be turned inwards so as to cover the teeth. The 

 play of the mouth, however, which contributes 

 in so eminent a degree to the expression of the 

 face, depends not only on the orbicularis, but 

 upon its association with the different muscles 

 which are attached around it. 



Naso-labialis is a small subcutaneous slip of 

 fibres, only distinctly seen in strong muscular 

 lips. It is situated on each side of the median 

 depression of the upper lip, and arises from 

 the lower septum of the nose at the back part 

 of the nostril ; it proceeds downwards and out- 

 wards, and is soon lost in the fibres of the or- 

 bicularis. It is an elevator of the middle part 

 of the upper lip, and is considered by some as 

 an attachment of the orbicularis. 



Levator labii superioris (l r , Jig. 134) is a 

 thin, flat, quadrilateral muscle, situated about 

 the middle of the face, and nearly on the same 

 plane with the levator labii superioris alaeque 

 nasi. It arises from the malar and upper 

 maxillary bones where they form three-fourths 

 of the lower border of the orbit, by short ten- 

 dinous slips ; from this origin the fibres, con- 

 verging a little, take a direction downwards 

 and inwards, and are inserted partly super- 

 ficially into the skin of the upper lip, and 

 partly into the fibres of the orbicularis, between 

 the insertion of the levator labii superioris 

 alaeque nasi and the lesser zygomatic, with 

 which its fibres are partly covered and con- 

 founded. 



Relations. Its anterior surface is covered 

 above by the orbicularis palpebrarum, below 

 by the skin and by the muscles with which its 

 fibres are mingled at its insertion. Its posterior 

 surface covers the infra-orbitar vessels and 

 nerves at their exit from the infra-orbitar fo- 

 ramen, which, with some fat and cellular tissue, 



separates it from the upper part of the levator 

 anguli oris. It covers also part of the trian- 

 gularis nasi. 



Its action is to raise and draw a little out- 

 wards the upper lip. 



Zygomaticus minor (3', fig. 134) is a narrow 

 rounded muscle, often wanting It arises from 

 the external surface of the os malae, and fre- 

 quently also from the deep fibres of the orbicu- 

 laris palpebrarum, by which its origin is co- 

 vered ; it proceeds downwards and inwards, 

 and is attached to the skin and orbicuiaris pal- 

 pebrarum above the commissure of the lips, 

 where its fibres are also confounded with those 

 of the levator labii superioris proprius. 



Relations. This muscle is covered in front 

 by the orbicularis palpebrarum and skin ; its 

 posterior surface conceals a part of the levator 

 anguli oris and of the labial vein. 



Action. It is an associate of the levator 

 labii superioris, and contributes to raise the 

 upper lip and draw it a little outwards. 



Zygomaticus major (3, Jig. 134), placed to 

 the outer side and 'a little below the preceding 

 muscle, is of a rounded form, and arises by 

 short tendinous slips from a depression on the 

 posterior part of the outer surface of the os 

 malse, near its lower border. Its fibres proceed 

 downwards and inwards, nearly parallel with 

 those of the lesser zygomatic, but much longer; 

 and expanding a little below, they become con- 

 founded with the fibres of the orbicularis oris 

 at their commissure, and with those of the 

 levator labii superioris, levator anguli oris, and 

 depiessor anguli oris. Its superficial fibres are 

 attached to the skin. 



Relations. This muscle is surrounded by 

 fat, which separates it from the skin. By its 

 deep surface it rests above on the os mala and 

 the masseter; below, it is separated by fat 

 from the buccinator and the levator labii supe- 

 rioris : it crosses also the labial vein. 



Its action carries the commissure of the lips 

 upwards and outwards, and is intermediate 

 between the action of the levator and the buc- 

 cinator : it is the antagonist of the levator an- 

 guli oris in drawing the lip outwards; its 

 associate in raising it. When both these mus- 

 cles act, the commissure of the lips is directly 

 raised . 



Levator anguli oris (musculus caninus) : (c, 

 fig. 136). To expose this, the levator labii 

 superioris must be removed. It is a flat qua- 

 drilateral muscle, which arises from the middle 

 of the canine fossa of the upper jaw, and be- 

 coming somewhat narrower takes a direction 

 downwards and a little outwards and forwards, 

 to terminate at the commissure of the lips, 

 where its fibres mingle with those of the orbi- 

 cularis, the buccinator, and the depressor 

 anguli oris. 



Relations. Deeply placed above, its ante- 

 rior surface is covered by the infra-orbitar ves- 

 sels and nerves, and by fat, which separate it 

 from the levator labii superioris and the lesser 

 zygomatic. Below it is covered by the zygo- 

 maticus major and the integument. The pos- 

 terior surface of this muscle rests on the upper 



