310 MUSCLES OF THE FACE. 



nator acts principally in front on the commissure of the lips, 

 which it draws backwards horizontally, increasing transversely 

 the aperture of the mouth, and throwing the cheek into the 

 vertical folds, so conspicuous in old age. It thus antagonizes 

 the orbicularis oris. If both these muscles act together, the 

 lips are extended and pressed against the teeth. When the 

 cavity of the mouth is distended with air or liquids, the fibres 

 of this muscle are protruded and curved. If the muscle now 

 acts, the fibres become straightened, and the fluid is expelled 

 from the mouth, suddenly or gradually, according to the resist- 

 ance made by the orbicularis. 



This muscle assists also in mastication and deglutition, by 

 pressing the food from between the cheek and gums into the 

 cavity of the mouth. 



2. Zygomaticus Major, 



Arises, fleshy, from the os malae, near the zygomatic suture. 



Inserted into the angle of the mouth, appearing to be lost in 

 the depressor anguli oris and orbicularis oris. 



Use. To draw the corner of the mouth and under lip 

 towards the origin of the muscle, and make the cheek promi- 

 nent, as in laughing. 



2. Zygomaticus Minor, 



Arises from the upper prominent part of the os malae, above 

 the origin of the former muscle ; and, descending obliquely 

 downwards and forwards, is 



Inserted into the upper lip, near the corner of the mouth, 

 along with the levator anguli oris. 



Use. To draw the corner of the mouth obliquely outwards 

 and upwards towards the external canthus of the eye. 



The common muscle is the 



Orbicularis Oris. 



This muscle is, in a great measure, formed by the muscles 

 that move the lips ; the fibres of the superior descending, those 



