448 LACHRYMAL APPARATUS. 



Occasionally an arch is formed between two of them, as is seen in 

 that figure, and produces a very graceful appearance. 



The edges of the eyelids are furnished with a triple row of long 

 thick hairs, which curve upwards from the upper lid, and down- 

 wards from the lower, so that they may not interlace with each 

 other in the closure of the eyelids, and prove an impediment to the 

 opening of the eyes. These are the eyelashes (cilia), important 

 organs of defence to the sensitive surface of so delicate an organ 

 as the eye. 



The Conjunctiva is the mucous membrane of the eye. It covers 

 the whole of its anterior surface, and is then reflected upon the lids 

 so as to form their internal layer. The duplicatures formed between 

 the globe of the eye and the lids are called the superior and inferior 

 palpebral sinuses, of which the former is much deeper than the in- 

 ferior. Where it covers the cornea the conjunctiva is very thin 

 and closely adherent, and no vessels can be traced into it. Upon 

 the sclerotica it -is thicker and less adherent, and to the inner sur- 

 face of the lids is very closely connected, and is exceedingly vas- 

 cular. It is continuous with the general gastro-pulmonary mucous 

 membrane, and sympathizes in its affections, as may be observed in 

 various diseases. From the surface of the eye it may be traced 

 through the lachrymal gland ; along the edges of the lids it is con- 

 tinuous with the mucous lining of the Meibomian glands, and at the 

 inner angle of the eye may be followed through the lachrymal 

 canals into the lachrymal sac, and thence downwards through the 

 nasal duct into the inferior meatus of the nose. 



This membrane is coated with a lamellated epithelium composed 

 of vesicles and flattened scales, with central nuclei. 



The Caruncula lachrymalis is the small reddish body which occu- 

 pies the lacus lachrymalis at the inner canthus of the eye. In 

 health it presents a bright pink tint ; in sickness it loses its colour 

 and becomes pale. It consists of an assemblage of follicles similar 

 to the Meibomian glands, embedded in a fibro-cartilaginous tissue, 

 and is the source of the whitish secretion which so constantly forms 

 at the inner angle of the eye. It is covered with minute hairs 

 which are sometimes so long as to be distinctly visible to the naked 

 eye. 



Immediately to the outer side of the caruncula is a slight dupli- 

 cature of the conjunctiva, called plica semilunaris, which contains 

 a minute plate of cartilage, and is the rudiment of the third lid of 

 animals, the membrana nictitans of birds. 



Vessels and nerves. The palpebrse are supplied internally with 

 arteries from the ophthalmic, and externally from the facial and 

 transverse facial. Their nerves are branches of the fifth and of the 

 facial. 



LACHRYMAL APPARATUS. 



The Lachrymal apparatus consists of the lachrymal gland with 



