CONJUNCTIVAL MUCOUS MEMBRANE. Ill 



closed. Nevertheless we are hardly conscious of an effort in 

 keeping the eyes open, in our waking moments, and we re- 

 quire an effort to close the eyes. During sleep, the eyes are 

 closed and the globes are turned upward. The contractions 

 of the orbicular muscles which take place in winking are 

 usually involuntary. This act occurs at short intervals, and 

 is useful in spreading the lachrymal secretion over the ex- 

 posed portions of the globes. The action of both sets of 

 muscles is usually symmetrical, though we may educate them 

 so as to close one eye while the other is kept open. The 

 action of the orbicularis is so far removed from the control 

 of the will, that when the surface of the globe is touched or 

 irritated, or when the impression of light produces intense 

 pain, it is impossible to keep the eye open. 



Conjunctiva! Mucous Membrane. The entire inner sur- 

 face of the upper and lower eyelids is lined by a mucous 

 membrane, which is reflected forward from the inner periph- 

 ery of the lids over the eyeball. The membrane lining the 

 lids is called the palpebral conjunctiva, and that covering 

 the eyeball, the ocular conjunctiva. The latter presents a 

 sclerotic and a corneal portion. The membrane presents a 

 superior and an inferior fold, where it is reflected upon the 

 globe. In the superior conjunctival fold, are numerous glan- 

 dular follicles, or accessory lachrymal glands, which secrete a 

 certain portion of the fluid which moistens the surface of the 

 eyeball. These are generally described as forming a portion 

 of the lachrymal gland. At the inner canthus, there is a ver- 

 tical fold, the plica semilunaris, with a reddish, spongy eleva- 

 tion at its inner portion, called the caruncula lacrymalis. The 

 caruncula presents a collection of f ollicular glands, with a few 

 delicate hairs on its surface. The conjunctiva is continuous 

 with the membrane of the lachrymal ducts, the puncta lacry- 

 malia, and the Meibomian glands. Beneath the conjunctiva, 

 except in the corneal portion, is a loose connective tissue. 



The palpebral conjunctiva is reddish, thicker than the 



