THE ARTERIES. 289 



opposite the condyloid process of the mandible. It enters the 

 mandibular canal by the mandibular foramen, along with the 

 nerve of the same name, and traverses the canal, furnishing 

 branches to the lower teeth. It emerges at the mental foramen, 

 and its terminal branches are distributed to the chin, but a 

 branch is continued in the bone beyond the mental foramen 

 and supplies the incisor and canine teeth of the lower jaw. 



2. A. meningea media (Fig. 120, k). The middle menin- 

 geal is a large vessel which leaves the internal maxillary at 

 about the same level as the inferior alveolar. It passes into 

 the foramen ovale and ramifies in the dura mater. Its branches 

 leave distinct impressions on the inner surface of the bones of 

 the skull. 



3. A large branch (Fig. 121, h) from the plexus passes 

 into the cranial cavity through the orbital fissure and lies 

 within the skull at the side of the hypophysis. It gives off 

 the following branches : 



a. A posterior communicating branch, very short, which 

 extends caudad and joins the internal carotid artery (Fig. 



12 !,.). 



b. A. cerebri media (Fig. 121, z). The middle cerebral 

 artery passes dorsad on the side of the cerebral hemisphere 

 along the fissure of Sylvius and divides into numerous branches 

 which are distributed to the surface of the cerebrum. 



c. A. cerebri anterior (Fig. 121,7') passes dorsad between 

 the cerebral hemispheres. Just craniad of the optic chiasma 

 the two anterior cerebral arteries are united by a small com- 

 municating branch, thus completing the circulus arteriosus or 

 circle of Willis (Fig. 121), surrounding the hypophysis (see 

 page 292). 



4. From the carotid plexus several branches pass, arising 

 either separately or in common, to the masseter, temporal, and 

 pterygoid muscles. 



5. A. ophthalmica (Fig. 120, n\ The ophthalmic artery 

 passes from the carotid plexus to the structures in the orbit. 

 It gives off numerous branches which supply the muscles of the 

 eyeball, and other structures of this region. It sends an 

 ethmoidal branch into the nasal cavity through the ethmoidal 



