THE HEAD AND NECK 1189 



In the vicinity of the closed ends of the Meibomian glands there 

 are some convoluted tubules, which are known as the posterior 

 tarsal, or accessory lachrymal, glands, the orifices of which are 

 placed close to the fornix conjunctivae. 



Conjunctiva. — ^This is the mucous membrane which covers the 

 ocular surfaces of the eyelids and the front of the eyeball. It 

 consists of two parts — palpebral and ocular. 



The palpebral conjunctiva lines the ocular or inner surfaces of the 

 eyelids, and, at their ciliary margins, it is continuous with the 

 skin on their outer surfaces. It is also continuous, through the 

 puncta lacrimalia, with the lining membrane of the lachrymal 

 canals, lachrymal sac, nasal duct, and inferior meatus of the nose. 

 In the region of the inner canthus it gives rise to the plica semi- 

 lunaris, and at the outer part of the upper eyelid it is continuous 

 with the lining membrane of the lachrymal ducts. The palpebral 

 conjunctiva is fairly thick and highly vascular, and it presents 

 numerous papillae. 



The ocular conjunctiva consists of two portions — sclerotic and 

 corneal. It is continuous with the palpebral conjunctiva, and the 

 line of reflection from the eyelids is known as the fornix conjunctivae, 

 superior and inferior respectively. In this vicinity the orifices of 

 the posterior tarsal, or accessory lachrymal, glands are met with. 

 The sclerotic conjunctiva covers the part of the sclerotic which is 

 adjacent to the cornea. It is loosely connected to the sclerotic, 

 is thin, non-papillary, and transparent, and contains only a few blood- 

 vessels, the whiteness of the sclerotic being unaffected by it. The 

 corneal conjunctiva is very thin, and consists only of the conjunctival 

 epithelium. 



The palpebral conjunctiva is covered by columnar epithelium, 

 which, at the ciliary margin, passes into the stratified epithelium 

 of the skin ; the sclerotic conjunctiva is also covered by colunmar 

 epithelium ; but the corneal conjunctiva is represented by the 

 stratified epithelium of the cornea. 



The conjunctiva is supplied with blood by offsets from the 

 palpebral branches of the ophthalmic artery and its lachrymal 

 branch. The vessels are disposed in a tortuous manner, and are 

 movable upon the eyeball when the conjunctiva is pressed upon 

 and displaced. The nerves are numerous, and form plexuses. 

 The lymphatics commence close to the corneal margin in a network, 

 from which vessels proceed to a network in each eyelid behind the 

 tarsal plate. The efferent vessels ultimately reach the parotid and 

 submaxillary lymphatic glands. 



The caruncula lacrimalis occupies the lacus lacrimalis in the 

 region of the inner canthus. It is a small, reddish, spongy bodv, 

 consisting of a detached portion of skin, containing modified sweat 

 and sebaceous glands. The latter open into the follicles of very 

 delicate hairs with which the surface of the caruncle is provided, and 

 they furnish the white secretion which may accumulate at the inner 

 canthus. 



