THE INTERNAL CAROTID ARTERY 613 



anterior fossa; it anastomoses with the clural branch from the posterior ethmoidal 

 artery. 



5. The ophthalmic artery (a. ophthahnica) arises from the internal carotid, 

 just as that vessel is emerging from the cavernous sinus, on the inner side of the 

 anterior clinoid process, and enters the orbit through the optic foramen, below and 

 on the outer side of the optic nerve. It then passes over the nerve to the inner wall 

 of the orbit and thence horizontally forward, beneath the lower border of the 

 Superior oblique muscle, to a point behind the internal angular process of the 

 frontal bone, where it divides into two terminal branches, the frontal and nasal 

 branches. As the artery crosses the optic nerve it is accompanied by the nasal 

 nerve, and is separated from the frontal nerve by the Rectus superior and Levator 

 palpebrae superioris muscles. 



Branches. The branches of this vessel may be divided into an orbital group, 

 which are distributed to the orbit and surrounding parts, and an ocular group, 

 which supply the muscles and globe of the eye: 



Orbital Group. Ocular Group. 



Lacrimal. Short ciliary. 



Supraorbital. Long ciliary. 



Posterior ethmoidal. Anterior ciliary. 



Anterior ethmoidal. Central artery of the retina. 



Internal palpebral. Muscular. 



Frontal. 



Nasal. 



The lacrimal (a. lacrimalis) is one of the largest branches derived from the 

 ophthalmic, arising close to the optic foramen ; not infrequently it is given off from 

 the ophthalmic artery before it enters the orbit. It accompanies the lacrimal 

 nerve along the upper border of the External lectus muscle, and is distributed to 

 the lacrimal gland. Its terminal branches, escaping from the gland, are distributed 

 to the eyelids and conjunctiva; of those supplying the eyelids, two are of consider- 

 able size and are named the external palpebral (aa. palpebrales laterales) ; they run 

 inward in the upper and lower lids respectively, and anastomose with the internal 

 palpebral arteries, forming an arterial circle in this situation. The lacrimal artery 

 gives off one or two malar branches, one of which passes through a foramen in 

 the malar bone, to reach the temporal fossa, and anastomoses with the deep tem- 

 poral arteries; the other appears on the cheek through the malar foramen, and 

 anastomoses with the transverse facial. A recurrent branch passes backward 

 through the sphenoidal fissure to the dura, and anastomoses with a branch of 

 the middle meningeal artery. 



Peculiarities. The lacrimal artery is sometimes derived from one of the anterior branches 

 of the middle meningeal artery. 



The supraorbital artery (a. supraorbital is) arises from the ophthalmic as that 

 vessel is crossing over the optic nerve. Ascending so as to arise above all the muscles 

 of the orbit, it passes forward, with the supraorbital nerve, between the periosteum 

 and Levator palpebrae muscle: and, passing through the supraorbital foramen, 

 divides into a superficial and deep branch, which supply the integument, the 

 n^scles. and the pericranium of the forehead, anastomosing with the frontal, the 

 aliterior branch of the temporal, and the supraorbital artery of the opposite side. 

 This artery in the orbit supplies the Superior rectus and the Levator palpebrae 

 muscles, and sends a branch inward, across the pulley of the Superior oblique 

 muscle, to supply the parts at the inner canthus. At the supraorbital foramen 

 it frequently transmits a branch to the diploe. 



