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, £).—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, %) 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. 
121, g). ; 
6. A. cerebri media (Fig. 121, 7).—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. 
53. A. ophthalmica (Fig. 120, ~).—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 
