58fi THE EYE. 



caruncula, and of the ocuiar parfc or conjunctiva bulbi, in which may 

 be distinguished the sclerotic and corneal portions : each of these parts 

 presents distinctive characters. The epithelium of the conjunctiva 

 varies somewhat at different parts, but is mainly columnar, with smaller 

 cells between the fixed ends of the columnar cells. Near the skin and 

 cornea it shades off into the stratified epithelium which covers these parts. 



The imlpchral 2)ortion of the conjunctiva is thicker and more vascular 

 than any other part of the membrane, and presents numerous fine papillre 

 freely supplied with nerves. It passes through the puncta lachrymalia 

 into the canaliculi, and is continuous with the lining membrane of the 

 lachrymal sac. Although closely united to the tarsi, it exhibits, never- 

 theless, numerous small creases or folds, which are visible with a lens. 

 A layer of small racemose or tnbulo-racemose glands is found on the 

 ocular surface of the lids, immediately under the conjunctiva, and be- 

 yond the ends of the Meibomian glands (Sappey, W, Krause). Their 

 minute ducts open near the line of reflection of the conjunctiva upon 

 the globe of the eye {fornix conjimctira). 



The sclerotic porf.mi. — The conjunctiva changes its character at the 

 line of reflection from the eyelids, becoming thinner and losing its 

 j)apillary structure : it is loosely connected to the eyeball by submucous 

 tissue. It is transparent and a few blood-vessels are generally visible in 

 it in the healthy condition, but under the influence of inflammatory 

 congestion a copious network of vessels very irregularly disposed comes 

 into view. These vessels are derived from the palpebral and laclu-ymal 

 arteries. 



Another set of vessels exists on the surface of the sclerotic, and 

 are seen when congested. These are entirely sub-conjunctival and 

 adherent to the sclerotic coat ; they are less tortuous than the con- 

 junctival set, and are derived from the muscular and anterior ciliary 

 branches of the ophthalmic arterj' : they remain immoveable on pressure 

 of the eyelid, whereas the conjunctival vessels of course shift with that 

 membrane. These sclerotic vessels dip in near the cornea, and appear 

 to unite with a deeper minute network disposed in closely set straight 

 lines, which radiate from the margin of the cornea, and the gorged con- 

 dition of which is well known to ophthalmic surgeons as characteristic 

 of sclerotitis. 



The corneal conjunctira consists almost entirely of epithelium, any 

 underlying membrane being extremely thin, transparent, and adherent 

 to the anterior layers of the cornea, in connection with which it will be 

 again referred to. Around the circumference A^essels lie between it 

 and the cornea, and form a circle of anastomotic capillary loops. This 

 plexus of vessels extends farther inwards in the fcetus. 



A -well developed network of h/nqyhnfics exists throughout the sclerotic and 

 palpebral portions of the conjunctiva : but at the margin of the cornea a sudden 

 diminution takes place in the size of the meslies and diameter of the vessels, 

 which become irregular, and come into connection with ramified cell-si^aces in 

 the cornea. 



The nerves in the membrane, as far as the cornea, seem to have the same 

 arrangement as in the skin. Their mode of ending has not been traced with 

 certainty, but according to Krause many of them tenninate in end-bulbs. 



The mucous membrane of the i^alpebral conjunctiva contains, especially at its 

 back part, a large quantity of lymphoid tissue. Ljnnphoid follicles have also 

 been described in the conjunctiva (Bruch). but their existence in man is doubtful 

 (Waldeyer). 



