THE EYE AND ITS APPENDAGES. 367 



The nervous supply of the several parts of the eye has already 

 been considered in detail ; it remains to add a short description of 

 their general relations. 



The long and short ciliary nerves pierce the sclerotic coat in 

 the vicinity of the optic nerve and pass between the sclera and the 

 choroid, giving off branches for the supply of the latter, and unite 

 to form the ciliary ganglionic plexus on the outer part of the 

 ciliary body. From this plexus twigs pass to the tissues of the ciliary 

 muscle, the iris, and the cornea, to be distributed in the manner 

 already described. 



THE APPENDAGES OF THE EYE. 

 THE EYELIDS. 



The eyelids are protecting folds which include between their 

 tegumental and mucous surfaces connective tissue, muscular and 

 glandular structures. The constituents of the eyelids are arranged 

 as general layers from without inward, these being : (i) the integu- 

 ment and subcutaneous tissue, (2) the muscular layer, (3) the 

 median connective tissue, (4) the tarsal plate, and (5) the con- 

 junctiva. 



The skin covering the external surface of the eyelid is thin, thrown 

 into folds, and beset with fine hairs and small sweat-glands ; the 

 corium possesses slightly-developed papillae, except at the edge of 

 the lid, where the fibrous tissue is denser and displays more conspic- 

 uous elevations. The constant occurrence of pigment-cells within 

 the corium is a noteworthy peculiarity. 



The loose subcutaneous tissue is rich in elastic fibres, but fat is 

 wanting, or, if present, is found only in meagre amount. At the 

 outer border of the margin of the lid large stiff hairs, the cilia, ex- 

 tend obliquely outward ; they are arranged as two or three rows, 

 their hair-follicles extending deeply into the corium and being sup- 

 plied with small sebaceous glands. The life of the cilia is short, 

 being about four months in duration ; as a result, hairs in all stages 

 of growth are usually included among the eyelashes. 



The muscular bundles of the orbicularis palpebrarum constitute 

 the layer next the subcutaneous tissue. At the lower margin of the 

 lid the muscle-bundles are divided by the outer structures occupying 

 this region ; an especially robust bundle separated by the lashes lies 

 near the posterior margin of the lid-edge and constitutes the ciliary 

 or marginal muscle of the lid. 



The succeeding connective-tissue layer is composed largely of 

 the fibrous extensions of the tendon of the levator palpebrae, 

 which are partly inserted into the areolar tissue fascia palpe- 



