708 THE EYE. 



Structure of the conjunctiva. The conjunctiva consists of the palpebral 

 part, along with which may be grouped the plica semilunaris and caruncula 

 lachrymalis, and of the ocular part or conjunctiva bulbi, in which may be 

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

 presents peculiar and distinctive characters. The epithelium is stratified and 

 thick ; the cells of the superficial strata scaly, delicate, and each with a 

 distinct nucleus. 



The palpebral portion of the conjunctiva is opaque and red, is thicker and 

 more vascular than auy other part of the membrane, and presents numerous 

 fine papillae freely supplied with nerves. At the margins of the lids 

 the palpebral conjunctiva enters the ducts of the Meibomian glands ; 

 through the pun eta lachrymalia it passes into the canaliculi, and is con- 

 tinuous with the lining membrane of the lachrymal sac ; and it is prolonged 

 into the orifices of the ducts of the lachrymal gland. 



The sclerotic portion of the conjunctiva, changing its character at the line 

 of reflection from the eyelids, becomes thinner, and loses its papillary 

 structure : it is loosely connected to the eyeball by submucous tissue. It is 

 also transparent and nearly colourless, but a few scattered branches of blood- 

 vessels are generally visible on it in the healthy condition, and under the 

 influence of inflammatory congestion a copious network of vessels very irre- 

 gularly disposed comes into view. This network is derived from the palpebral 

 and lachrymal arteries. It may be easily made to glide loosely on the sur- 

 face of the eyeball by pressing the eyelid against it. But another set of 

 vessels likewise exists on the surface of the sclerotic, and may be brought 

 into view by congestion. The position of this set is entirely sub-conjunc- 

 tival, adherent to the sclerotic coat ; they are less tortuous than the conjunc- 

 tival set, and are derived from the muscular and anterior ciliary branches of 

 the ophthalmic artery : they remain immoveable on pressure of the eyelid. 

 They dip into the sclerotic near the cornea, and appear to unite with a more 

 deeply connected minute network disposed in closely set straight lines, 

 radiating from the margin of the cornea, and the gorged condition of which 

 is well known to ophthalmic surgeons as characteristic of sclerotitis. 



The corneal conjunctiva consists almost entirely of epithelium, any under- 

 lying membrane being extremely thin, transparent, and adherent to the 

 anterior elastic layer of the cornea, in connection with which it will be again 

 referred to. Vessels lie between it and the cornea, and form a circle of 

 anastomotic capillary loops around the circumference. This plexus of 

 vessels extends farther inwards in the foetus. 



A well developed network of lymphatics 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 meshes and diameter of the vessels. Of the network 

 referred to, only a narrow circle ~th of an inch in diameter exists on the corneal 

 conjunctiva, and this circle has a well defined inner margin within which no lym- 

 phatics exist (Teichmann). 



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

 ment as in the skin in general. 



In the submucous tissue of the eyelids there are small follicular glands spread over 

 the whole surface of the conjunctiva palpebrarum, and in the vicinity of the reflection 

 of the conjunctiva upon the eyeball a set of larger more complex glands of a racemose 

 structure, somewhat similar to that of the lachrymal gland (Sappey, C. aud W. 

 Krause). 



Closed follicles have also been observed in the conjunctiva by Bruch, and, after 

 him, by other observers. 



