380 JAMES ROLLIN SLONAKER 



description of the circulation of the pecten is given when deahng 

 with this organ. 



The other artery which supphes the eye is the ophthalmic 

 (fig. 15, Op I). As already described, it arises from the internal 

 carotid artery (fig. 12, Op I). After reaching the orbit it bends 

 over the dorsal side of the optic nerve- and passes in a fairly 

 straight course to the anterior portion of the orbit. Here it 

 divides and leaves the orbit as the facial (F) and nasal (N) 

 arteries. In its course through the orbit it gives off a few 

 branches, one of which anastomoses with the branches of the 

 external ophthalmic and also supplies the internal rectus with a 

 few vessels. A little farther on it sends branches to Harder' s 

 gland and the superior oblique muscle. 



The arrangement of the veins of the eye is very similar to that 

 of the arteries. The front of the eye is supplied by the external 

 facial (fig. 13, EF). The names of the branches and their dis- 

 tribution are so like those of the arteries that it will be unneces- 

 sary to describe them. The distribution of the veins over the 

 posterior part of the eye differs in some respects from that of 

 the arteries (fig. 17). The ophthalmotemporal vein (OpT) 

 divides into two large branches which pass the optic nerve on 

 opposite sides. The anterior branch unites with the ophthalmic 

 vein {Op V), the posterior branch receives two veins from the 

 pecten, and then swings around under the nerve to unite with 

 the ophthalmic near the union of the anterior branch. There 

 is thus formed a venous circle around the optic nerve similar to 

 that formed by the arteries. 



The ophthalmic vein has a somewhat different course and 

 different branches from the ophthalmic artery. It enters the 

 orbit in the same region that the artery leaves it, and receives 

 blood from the superior oblique, Harder's gland, the internal 

 rectus and from the ophthalmotemporal vein. It passes anterior 

 and ventral to the optic nerve and leaves the orbit at the lower 

 side. 



