BRA.XCHES OF OPHTHALMIC 499 



it is described by some aiuituiuists as a fourth portion — the intracereln'al (fig. 387). 

 As it Ucs in the foramen lacerum mediinn the artery is erossed on its outer side by 

 the great superficial j)etrosal nerve as the latter goes to join the great deep petrosal 

 from the carotid plexus to form the Mdian nerve. 



Branches of the Internal Carotid Artery 



The cervical portion gives off no branch. The intraosseous portion gives 

 off: — (1) Tympanic; (2) Vidian. The intracranial portion gives off: — (1) 

 Arteria receptaculi; (2) pituitary; (3) Gasserian; (4j meningeal; (5) ophthalmic; 

 (6) posterior communicating; (7) anterior choroid; (8) anterior cerebral; (9) 

 middle cerebral. 



Branches of the Intraosseous Portion. — (1) The tympanic enters the tympanum 

 through a small foramen in the posterior "wall of the carotid canal, and contributes 

 its quota to the Ijloocl-supply of that cavity. It anastomoses Avith the tympanic 

 branches of the stylo-mastoid and internal maxillary arteries. (2) A Vidian 

 branch is also descriljed, and is said to anastomose Avith the Vidian artery. 



Branches of the Intracranial Portion. — As the internal carotid artery lies on tlie 

 inner side of the cavernous sinus, it gives off the following branches : — (1) Arteria 

 receptaculi, small branches to the walls of tlie cavernous sinus; (2) pituitary 

 branches to the pituitary body; (3) Gasserian or ganglionic branches to the 

 Gasserian ganglion; (4) meningeal or anterior meningeal branches to the dura 

 mater; these anastomose with anterior liranches of the middle meningeal. 



(o) THE OPHTHALMIC ARTERY 



The ophthalmic artery (fig. 339) comes off from the internal carotid imme- 

 diately bel(JW the anterior clinoid ])rocess just as the latter vessel is passing through 

 the dura mater. Entering the orljit through the optic foramen l^elow and external 

 to the optic nerve, it at once perforates the sheath of dura mater which is prolonged 

 through the optic foramen on both artery and nen'e. It then runs in a gentle curve 

 with its convexity outwards below the optic nerve and external rectus, being here 

 crossed by the nasal nen'e, and turning forwards, inwards, and upAvards, passes 

 over the optic nerve, round which it thus forms a loop (fig, 339) to the inner side 

 of the orbit. Thence it runs obliquely beneath the superior rectus in front of the 

 nasal nerve under the lower border of the superior oVilique, but above the internal 

 rectus, and continues its course under the pulley for the superior oblique and 

 reflected tendon of that muscle to the internal angular process of the orbit, where 

 it divides into the frontal and nasal branches. 



Branches of the Ophthalmic Artery 



The branches of the ophthalmic artery are: — (a) the lachrymal; (h) the 

 supra-orl)ital; {c) the central artery of the retina; (d) the muscular; (f) the ciliary; 

 (/) the posterior ethmoidal; ((/) the anterior ethmoidal; (A) the palpebral; (?) 

 the frontal; and (/.) the nasal. 



(a) The Lachrymal Artery 



Tiie lachrymal artery is usually the first and at times the largest l)ranch of the 

 0])lithalmic. It arises l)etween the superior and external rectus on the outer side 

 of the optic nerve from the ophthalmic soon after that vessel has entered the orbit. 

 At times it is given off from the ophthalmic outside the orbit, and then usually 

 passes into that cavity through the si)lienr)idal fissure. It runs forwards along the 

 outer wall of the orbit with the lachrymal nerve above the upper border of the 

 external rectus to the lachrymal gland, which it supplies. In tliis course it fur- 

 nishes the following branches: — (i) Recurrent lachrymal, one or more branches 

 Avhich pass backwards through tiie splienoidal fissure, and anastomoses with the 

 lachrymal branch of tlie large middle meningeal artery. The anastomosis is some- 



