MUSCLES OF THE FACE. 369 



The Orbicular is 0m, 



Is a circular musclejust beneath the skin, much blended with 

 adipose matter externally, but more plain on the surface conti- 

 guous to the lining membrane of the mouth. It constitutes a 

 considerable part of the thickness of the lips, and surrounds 

 the mouth entirely. It has no bony origin, but arises from the 

 fibres of the several muscles which join each other at the cor- 

 ner of the mouth, and therefore consists of two semicircular 

 planes, one for the upper and the other for the lower lip. 



It is the antagonist to most of the other muscles of the mouth. 

 From its superior part a pyramidal slip goes to the tip of the 

 nose, being called, by Albinus, Nasalis Labii Superioris. 



Masseter. 



The masseter is placed between the skin and the ramus of 

 the lower jaw; it is of an oblong shape, and evidently consists 

 of two portions, an external and an internal, which may be 

 readily recognised by the course of their fibres as they decus- 

 sate. 



As a whole, it arises, tendinous and fleshy, from the malar 

 process of the maxillare superius; from the inferior edge of the 

 malar bone, between the maxillary and the zygomatic sutures, 

 and from the zygomatic process of the temporal bone. Of its 

 two portions, the internal is the smaller, and is inserted tendi- 

 nous into the outer part of the root of the coronoid process of 

 the lower jaw; while the external extends from the malar bone 

 to the angle of the lower jaw, where it is inserted tendinous 

 and fleshy. A part of the internal portion may be seen at the 

 zygomatic suture, behind the external, without the latter being 

 raised up. 



When both portions act together, they close the jaws: the 

 external, alone, also draw's the jaw forwards; and the internal, 

 alone, will also draw it backwards. 



