ANATOMY OF THE EYE 27 



from the optic disk to the posterior lens capsule. In 

 some cases portions of this persist, with an opacity of 

 the central portion of the posterior capsule, known as a 

 posterior polar cataract. 



Should the vitreous become fluid, as it sometimes does 

 by reason of disease, the tension of the globe is much de- 

 creased and the retina may become detached by loss of 

 support. 



The conjunctiva is a mucous membrane, and covers 

 the anterior half of the globe, except that portion sup- 

 plied by the cornea. It merges with the anterior epi- 

 thelium of the cornea, extending over the sclera as far 

 as the fornix, where it folds upon itself and Hues the 

 posterior surface of the lid, and is strongly adherent to 

 the tarsus. This portion is called the palpebral conjunc- 

 tiva. The bulbar portion is freely movable over the 

 sclera, and is connected to it by the loose episcleral tis- 

 sue. At the inner angle, in man, is a fold known as the 

 plica semilunaris, which is said to be a rudimentary 

 nictitans membrane so prominent in animals. Just 

 inside of this is a small elevated island of tissue covered 

 with hairs, known as the caruncle. 



The nictitans membrane, or ''accessory eyehd," is 

 situated near the nasal angle, between the globe and the 

 side of the orbit. It is composed of elastic fibrocartilage 

 and is irregidar in form, being thick and somewhat 

 prismatic at its base and thin anteriorly, where it is cov- 

 ered with a fold of conjunctiva. Posteriorly, it is con- 



