674 THE EYE 



anterior set of lymphatic vessels, but from the vitreous 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 addition to the optic, are the long and 

 short ciliary branches of the ophthalmic nerve. The former, two or 

 three in number, and the latter, six to ten, after supplying a vasomotor 

 branch to the arteria centralis retinae, pierce the sclera in company with 

 the corresponding ciliary arteries and pass meridionally forward on the 

 inner surface of the sclera, supplying branches to this tunic and to the 

 vessels of the choroid, and finally reaching the ciliary muscle, where 

 their branches form an annular plexus containing a few ganglion cells. 



From this plexus fibrils are supplied to the blood-vessels and mus- 

 cular tissues of the ciliary body and iris, and to the cornea. The corneal 

 branches pass to the annular plexus at the sclerocorneal junction, whence 

 they are distributed to the corneal tissues, as already described (page 

 633). 



APPENDAGES OF THE EYE 



The appendages of the eye include the eyelids, conjunctiva, and 

 lacrimal glands. 



THE EYELIDS 



The eyelids are developed in the embryo through an invagination of 

 the skin, which, leaving a slit-like aperture (the palpebral fissure) 

 between its involuted margins, covers the inner surface of the lid to 

 form the palpebral conjunctiva, and is reflected over the globe of the 

 eye as the ocular conjunctiva and anterior corneal epithelium. 



The lids, therefore, may be said to consist of two membranous por- 

 tions, the cutaneous (outer or anterior) and the conjunctival (inner or 

 posterior). Between these two portions the orbicularis palpebrarum 

 forms a septum of striated muscle fibers. 



The cutaneous portion of the eyelid differs from other portions 



