374 HISTOLOGY. 



teriorly the tissue spaces include the hyaloid canal of the vitreous body; 

 the very narrow perichorioideal space between the chorioid and sclera; 

 the subdural and subarachnoid spaces of the optic sheaths, named the 

 intravaginal spaces; and finally the interfascial space [of Tenon] which 

 surrounds most of the sclera and is prolonged as a supradural space around 

 the. optic nerve. These spaces may be filled from the subarachnoid of 

 the brain. They contain a "filtrate from the vessels." The interfascial 

 and perichorioideal spaces hold but little fluid; acting as bursae, they may 

 facilitate the movements of the eye. 



NERVES. 



Apart from the optic nerve, the eye is supplied by the short ciliary 

 nerves from the ciliary ganglion, and the long ciliary nerves from the naso- 

 ciliary branch of the ophthalmic nerve. The ciliary nerves penetrate the 



sclera near, the optic nerve and 

 send branches containing gang- 

 lion cells to the vessels of the 

 chorioid. The nerves pass for- 

 ward between the chorioid and 

 sclera to the ciliary body, where 

 they form a circular ganglionated 

 P ropna. a I ~~ ^ M plexus, the plexus ganglwsus 



FIG. 426. FROM A SECTION OF THE HUMAN CORNEA. ClliariS. Its branches extend to 



* 24 ' (i) the ciliary body, (2) the iris 



n, A dividing nerve penetrating the anterior basal 



membrane; s, subepithelial plexus beneath the and ("?) the COmea. 



cylindrical cells; a, fibers of the intraepithelial 



plexus ascending between the epithelial cells. The nerVCS of the ciliary 



body form a delicate network on 



its scleral surface, they supply its muscle fibers and those of the vessels 

 with slender motor endings, and between the ciliary muscle bundles they 

 have branched free endings, perhaps sensory. 



The medullated nerves of the iris lose their myelin and form plexuses 

 as they pass toward the pupillary margin. A sensory plexus is found just 

 beneath the anterior surface, and motor fibers supply the sphincter, 

 dilator and vascular muscles. The existence of ganglion cells in the human 

 iris is denied. 



The nerves of the cornea enter it from the plexus annularis in the 

 sclera just outside. The annular plexus also sends fibers into the conjunc- 

 tiva, where they end in networks, and in bulbous corpuscles (Fig. 128, 

 p. 106) situated in the connective tissue close to the epithelium. Such 

 corpuscles may be found i or 2 mm. within the corneal margin. The 

 corneal nerves become non-medullated and form plexuses between the 



