226 BLOOD VESSELS SUPPLYING THE ORGANS OF PREHENSION, 



round masses, which separates it from the masseter muscle 

 and ramus of the lower jaw, and by the zygomatic, the 

 levator, and depressor anguli-oris muscles, together with 

 the facial nerves and vessels which ramify over its surface. 

 The duct of Steno is seen passing through this muscle 

 at its upper part, opposite the second molar tooth of the 

 upper jaw. 



Orbicularis-oris consists of two semi-circular fleshy planes, 

 surrounding the mouth, intersecting each other at the an- 

 gles, and blending with all the muscles already described. 

 It has one leading peculiarity in having no bony origin or 

 insertion. Its function is to close the mouth and antagonize 

 all the muscles inserted into its angles. This muscle con- 

 stitutes the chief thickness of the lips, and is intermixed 

 with small granulated particles of fat. 



COMBINED ACTION OF MUSCLES. 



The separate action of the several muscles concerned in 

 prehension, is, as we have seen, to elevate, depress, re- 

 tract, and close the lips ; while in their conjoint and har- 

 monious action, they either act separately or together, or 

 in whatever way may best accomplish the great end for 

 which they were designed. They are also engaged in other 

 functions, as speaking, breathing and mastication. 



BLOOD VESSELS SUPPLYING THE ORGANS OF PREHENSION. 



1. Facial Artery. 2. Infra Orbitar. 3. Transverse Facial. 



The Facial Artery (Fig. 73) arises from the external 

 carotid, at its front part, above the lingual, and ascends 

 to the submaxillary gland behind, by which it is covered. 

 It now curves over the base of the lower jaw, anterior to 

 the masseter muscle, ascends to the commissure of the lips, 

 thence by the side of the nose to the angle of the eye, 

 where it terminates by anastomosing with the ophthalmic. 

 Its whole course is very tortuous, to adapt it to the various 

 movements of the jaws. 



Its branches are, the inferior palatine, submaxillary, 



