SENSITIVE SVSTEiAl. 365 



Of the Appendages. 



Regarded in a general view in relation to their several func- 

 tions, the appendages will be found to answer the subsidiary 

 purposes to the eye itself of p/o/ec^/o//, motion, and abstersion. 



The appendages comprise — t/ie ei/eOroivs ; the eyelids; the 

 eyelashes; the muscles of the eyelids ; the tarsal cartilages ; the 

 meibomian glands ; the tunica conjunctiva ; the membrana nidi- 

 tans ; the lachrymal gland ; the caruncula lachrymalis ; the 

 puncta lachrymalia ; the lachrymal sac ; the ductus ad nasum ; 

 and the muscles of the eyeball. 



Eyebroio. 



The snperciHum or eyebrow is a part which characteristically 

 attracts attention in man, but one that is denied to animals*. 

 It is that ornamental arched eminence, clothed with hair, upon 

 the superciliary ridge of the frontal bone, which forms so striking 

 a feature and marks such expression in the human countenance, 

 while it serves as a shade to protect the eye from descending 

 glares of light, and from foreign bodies coming in the same di- 

 rection. Although eyebroxus are not allowed to the horse by 

 writers, the elevations formed by the orbital processes of the 

 frontal bones have similar relation to the eyes to what the same 

 parts have in man ; and these eminences, in addition to their 

 common pilous coverings, are furnished with many long hairs, 

 which, though they are rather stragglingly planted, for the most 

 part slant outivard and are disposed in arches : call them, there- 

 fore, by what name we may, they are evidently designed to in- 

 tercept vivid rays of light, and any foreign matters descending 

 upon the eye. 



Eyelids. 



The palpebra or eyelids are the moveable curtains in front of 

 the eye occupying the space comprehended within the circular 

 ridge of the orbit. There are two of them ; — an upper and a 

 lower lid. The upper being much the larger and more moveable 

 one, will cover a proportioiiably broader segment of the eyeball. 

 Both being capable of retraction and expansion, we find them in 

 the former or ordinary state, particularly the upper, drawn into 

 wrinkles, which run in curves, and have some etiect in the ex- 



* No animals have eyebrows. In the human species it is an organ of 

 expression ; well known as such to painters, who by a little arrang'ement 

 in the eyebrow can make great alteration in the expression of the coun- 

 tenance, which same alteration they cannot produce by the variation of 

 any other feature. — Abernelhif's Lectures. 



