EYE 



461 



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

 sclera near the optic nerve and send branches containing ganglion cells 

 to the vessels of the chorioid. The main stems pass forward between the 

 chorioid and sclera to the ciliary body, where they form a circular gang- 

 lionated plexus, the plexus gangliosus ciliaris. Its branches extend to 

 the ciliary body, the iris and the cornea, and are described as follows: 



The nerves 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. 154, 

 p. 160) 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 

 lamellae throughout the stroma. They extend into the epithelium and 

 there form a very delicate plexus with free intercellular endings. 



Substantia \ 



propria. I 



FIG. 468. FROM A SECTION OF THE HUMAN CORNEA. 

 X 240. 



n, A branching nerve penetrating the anterior basal 

 membrane; s, subepithelial plexus beneath the 

 cylindrical cells; a, fibers of the intraepithelial 

 plexus ascending between the epithelial cells. 



EYELIDS. 



The eyelids or palpebrce (Fig. 469) are covered with thin skin pro- 

 vided with fine lanugo hairs; small sweat glands extend into the corium, 

 which here contains pigmented connective tissue cells. The subcutaneous 

 tissue is very loose, having many elastic fibers and few or no fat cells. 

 Near the edge of the lid there are two or three rows of large hairs, the 

 eyelashes or cilia, the oblique roots of which extend deep into the corium. 

 Since they are shed in from 100 to 150 days they occur in various stages of 

 development. They are provided with small sebaceous glands, and the 

 ciliary glands (of Moll) open close beside or into their sheaths. The ciliary 

 glands are modified sweat glands, with simpler coils, which may show 

 successive constrictions ; " a branching of the tubules has been observed." 



