APPENDAGES OF THE EYE 601 



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

 vaso-motor branch to the arteria centralis retinae, pierce the sclera 

 in company with the corresponding ciliary arteries and pass me- 

 ridionally 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 

 muscular tissues of the ciliary body and iris, and to the cornea. 

 The corneal branches pass to the annular plexus at the sclero- 

 corneal junction, whence they are distributed to the corneal tissues, 

 as already described (page 569). 



APPENDAGES OF THE EYE 



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

 lachrymal glands. 



THE EYELIDS. The eyelids are developed in the embryo 

 as an invagination of the skin, which, leaving a slit-like aperture 

 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 

 portions, the cutaneous (outer or anterior) and the conjunctival 

 (inner or posterior). Between these two portions the orbicularis 

 palpebrarum forms a septum of striated muscle fibres. 



The cutaneous portion of the eyelid differs from other portions 

 of the skin only in that its subcutaneous tissue contains no fat. 

 The derma is loosely connected with the muscle by a wide-meshed 

 areolar tissue. Fine hairs are distributed over the cutaneous sur- 

 face, their follicles extending well down through the derma. 

 Small sebaceous glands open into the hair follicles and occasional 

 sudoriparous glands pour their secretion upon the epidermal surface. 



At the margin of the lid its cutaneous portion is reflected in- 

 ward, and at its inner angle becomes directly continuous with the 

 palpebral conjunctiva. The free margin of the lid presents, 

 therefore, an outer angle, an inner angle, and an intermediate sur- 

 face. 



Two or three rows of large stiff hairs, the eyelashes, project 

 from the outer angle, and large sebaceous glands open into their 

 follicles. Other smaller sebaceous glands open directly upon the 

 free surface. 



