600 THE EYE 



ing through the veins of the choroid and the venae vorticosae. 

 Some, however, is returned by means of anastomoses with the 

 anterior ciliary veins. 



4. The anterior ciliary arteries, derived from the muscular and 

 lachrymal branches of the ophthalmic, distribute branches to the 

 conjunctiva and sclera, and within the latter membrane, about 2 mm. 

 outside of the corneal margin, pass to the circulus iridis major and 

 partially supply the iris and ciliary body as already described. 



The anterior ciliary veins follow the course of the corresponding 

 arteries. They empty into the vessels of the ocular conjunctiva. 



THE LYMPHATIC SYSTEMS OF THE EYE. The lymphatic 

 systems of the eye include very few true lymphatic vessels, but 

 rather consist of a series of channels which may be arbitrarily con- 

 sidered as an anterior and a posterior set of intercommunicating 

 spaces. The former set includes the lymphatic spaces of the cornea, 

 the spaces of Fontana, the anterior and posterior chambers, the 

 lymphatic clefts of the ciliary muscle and iris, and the spatia zonu- 

 laris. The posterior set includes the subdural and subarachnoid 

 spaces in the sheath of the optic nerve, the capsule of Tenon, the 

 lymphatic spaces of the lamina suprachoroidea, the perivascular 

 spaces of the choroid and retina, the irregular clefts between the 

 pigmentary and bacillary layers of the retina, the similar clefts of 

 the ganglion cell layer, the lymphatic spaces of the hyaloid mem- 

 brane, and the interstices of the vitreous humor. 



These two sets of lymphatic channels communicate with each 

 other by means of the perivascular spaces of the two outer tunics, 

 as well as through that portion of the hyaloid membrane which 

 forms the posterior wall of the spatia zonularis, through the clefts 

 of which the lymph of the vitreous body communicates freely with 

 the aqueous humor of the spatia zonularis and posterior chamber. 

 Consequently, if the cornea be penetrated either accidentally or 

 otherwise, and the anterior and posterior chambers be emptied, 

 their aqueous humor is rapidly replaced, not only from the adjacent 

 spaces of the anterior set of lymphatic vessels, but from the vitre- 

 ous humor and posterior set as well. 



It is also important to note that the posterior set of lymphatic 

 spaces is directly connected through the meningeal sheaths of the 

 optic nerve with the subdural and subarachnoid spaces of the 

 cerebral meninges. 



THE NERVES OF THE EYE. The nerves of the eye, in addi- 

 tion to the optic, are the long and short ciliary. The former, two 



