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. 121, _g_). _b._ =A. cerebri media= (Fig. 121, _i_).--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, _j_) Passes dorsad between the cerebral hemispheres. Just craniad of the optic chiasma the two anterior cerebral arteries are united by a small communicating 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 foramen in the orbital plate of the frontal bone, then continues distad to emerge from the orbit on the medial side of the eye; here it anastomoses with branches of the superficial temporal. 6. =A. palatina minor= (Fig. 120, _p_).--The lesser palatine artery leaves the internal maxillary distad of the carotid plexus, near the caudal border of the maxillary bone. It passes ventrocaudad into the soft palate. 7. =A. sphenopalatina.=--The sphenopalatine is one of the terminal branches of the internal maxillary; it passes mediad through the sphenopalatine foramen into the nasal cavity, and divides into numerous branches which supply the mucous membrane of the nose. It gives off just before it enters the sphenopalatine foramen the =descending palatine= (=A. palatina descendens=), which passes into the posterior palatine canal and emerges on the surface of the hard palate, where it ramifies. 8. =A. infraorbitalis= (Fig. 120, _o_).--The infraorbital artery is a direct continuation craniad of the internal maxillary. It sends off numerous small branches to the teeth of the upper jaw, and a rather large branch which passes to the lower eyelid. It then enters the infraorbital foramen, at the same time dividing usually into two or three branches; these emerge from the foramen and supply the parts of the nose and upper lip adjacent to the foramen (Fig. 131, _r_). A. SUBCLAVIA. THE SUBCLAVIAN ARTERY.