35 



any, thins; from getting into the eye, when opeiu These 

 hairs only grow to a convenient length, and their 

 points stand out of the way, those of the upper eye- 

 lids being bent upward, and those of the lower, down- 

 ward. Mean time the eye-brows hinder sweat, or any 

 thing else which might be hurtful, from falling down 

 from the forehead. 



Both the eye-lids are moveable; but chiefly the 

 upper. Animals which have hard eyes, as lobsters, 

 need none, and therefore have no eye-lids. But most 

 brutes have an additional eye-lid (called the nictitating 

 membrane) which draws like a curtain, to wipe off 

 what might incommode the eye. The monkey indeed 

 has it notj as being furnished with hands like a 

 man. . ' 



23. The eye can move upward, down ward; to either 

 side, and round, either toward the right or left. For 

 these six motions, six muscles are allotted, wfrich 

 spread their tendons far into the eye. At each inner 

 corner of the eye, there is a gl ind with two or three 

 ducts, which opening on the inner surface of the eye-lid, 

 keep the eye-bail moist, to facilitate its motion. By 

 these glands, tears also are secerned, The eye is con- 

 nected with the surrounding bones by the tunica ad. 

 nata, commonly call the white of the eye, in the 

 midst of which is a large hole for the tunica cornea, 

 through which the iris and pupil appear. The whole 

 ball of the eye rises from the optic nerve, aiu! is 

 formed of three coats* propagated from it.aucl as many 

 Lumours, two of which, have each a. coat of us own 

 also. The eye therefore has five coats iu all : three 

 common, and two to contain their several humours. 



24. The outermost coat, proceeding from the dura 

 mater, and surro ndm^ the whole eye, is termed the 

 sclerotica ; the >;e part of it being transparent like 

 horn, is thence -styled the cornea. Tnis. is more con* 

 vex than the tvs. . ^f the eye. It is composed of seve- 

 ral parallel pnut*, w i.ea <uo nourished by many 



c 6 



