BLOOD-VASCULAR SYSTEM OF THE LORICATI 83 



The ophthalmic vcm proper (Pis. I, II and III, figs, i, 5, 13, 

 15 and 19; Oph.V.) arises as a sinus-like vessel from the dor- 

 sal region of the anterior horn of the choroid sinus, but grad- 

 ually tapers down into its caudal course, and when immediately 

 ventrad of the optic nerve receives a much smaller branch from 

 the posterior horn. Curving around to the posterior side of the 

 optic nerve it penetrates the silver layer of the choroid and the 

 sclerotic coat. Once outside of the eyeball the ophthalmic vein 

 pursues an oblique dorsal course, and, passing between the su- 

 perior and external recti muscles it unites with the rectus and iris 

 veins to form the internal jugular. 



Iris or Ophthalmic Minor Veins (PL II and III, figs. 13, 

 15 and 19 ; Ir.V.). — A single iris vein arises from the capillar- 

 ies in the dorsal part of the iris. Together with the ramus cil- 

 iaris longus and the iris artery it passes ventrad a short distance, 

 between the silvery and vascular layers of the choroid (see fig. 

 19), and then penetrates the silvery layer and the sclerotic coat. 

 After running along the posterior dorsal surface of the eyeball 

 it passes between the superior and external recti muscles, but 

 laterad to the ophthalmic vein. In its caudal course it receives 

 a branch from the external rectus muscle, and finally terminates 

 by uniting with the rectus and ophthalmic veins to form the 

 internal jugular. 



Optic or Retina Vein (PI. Ill, figs. 19 and 20; Opt.V.). — 

 In the specimen from which figs. 19 and 20 were drawn I 

 noticed a small vein penetrating the sclerotic coat just ventrad 

 of the optic artery. Its connection with the larger vessels had 

 been destroyed before the vein was noticed, and internally the 

 vein was not injected. Several specimens were injected espe- 

 cially to demonstrate this vessel, but in every case this vein 

 failed to become injected. It is probable, however, that this 

 vein follows the course of the optic artery, returning the venous 

 blood from the lens, falciform process, and the retina, and very 

 likely empties into the ophthalmic vein. 



As has already been stated in the first paragraph under {p) 

 the internal jugulars are connected with one another by a sinus- 

 like vessel, which crosses the eye-muscle canal. Leaving the 

 eye-muscle canal with the ciliary nerve and the iris artery. 



