262 OPHTHALMIC ARTERY. 



is continued through the vitreous humor to the capsule of the 

 crystalHne lens. 



3. While the ophthalmic is passing over the optic nerve the 

 branches which enter the ball of the eye leave it. Their number 

 varies, but they form three classes, viz. The Long Ciliary, the 

 Short Ciliary, and the Anterior Ciliary arteries, (see descrip- 

 tion of the eye,) the supra orbitary and muscular branches leave 

 it also near the same place. 



4. The Supra Orbital Branch often gives off several mus- 

 cular twigs: but it passes out of the orbit through the supra 

 orbitar foramen, and generally divides into two branches, one of 

 which is spent upon the periosteum, and the other upon the skin 

 and muscles of the forehead. 



5. There are sometimes two muscular branches, a Superior 

 and an Inferior. The superior branch is often deficient : 

 when it exists it supplies the levator palpebrae, the levator 

 oculi, obliquus superior, &c. ; but these parts are often sup- 

 plied by the branches above mentioned. The supra orbitar so 

 frequently gives off branches to the muscles, that it has been 

 called the Superior Muscular Branch. The inferior muscular 

 branch is more constant. It commonly supplies the rectus 

 inferior, the abductor, and the inferior oblique muscles, and also 

 the lachrymal sac, and the lower eyelid, Sic. 



When the artery is on the inside of the nerve it sends off the 

 two branches to the cavity of the nose, viz. The Ethmoidal 

 Arteries ; and, also, branches to the eyelids. 



6. The Posterior Ethmoidal branch is first. It passes 

 between the- levator and abductor muscles, and above the 

 obliquus seperior, and penetrates the cavity of the cranium by 

 the posterior orbitary foramen : after giving some twigs to the 

 dura mater, it passes to the posterior cells of the ethmoid by 

 the foramina of the cribriform plate of that bone, and sends a 

 small branch to the Schneiderian membrane on the back part of 

 the septum of the nose. 



7. The Anterior Ethmoidal artery arises from the ophthal- 

 mic nearly opposite to the anterior orbitary foramen, through 

 which it passes : and after entering the .cranium is distributed 



