MUSCLES AiVD PARTS CONNECTED AVITH THE EYE. 203 



beautifully proves design in tne formation and adaptation ot 

 the animal. The eyelashes should on no account whatever 

 be cut, as they have a most important office to fill, not only 

 preventing the eye from being injured by dazzling light, but 

 also protecting it from the intrusion of insects. 



The horse is destitute of eyebrows, but in their stead he 

 is provided with a number of scattered bristly hairs, as alse 

 a projecting fold of the upper eyelid, w4iich answers the 

 same purpose. Some persons are so foolish as to cut off 

 these hairs, and have absurdly attributed them to weakness. 

 The under eyelid also is furnished with projecting bristly 

 hairs, which are so sensitive that they give immediate Avarn- 

 ing to the animal of the approach of any insect or other 

 object w^hich might injure the eye, and he naturally closes 

 the eyelid instantaneously. Ignorant grooms sometimes 

 denude horses of these admirable premonitory feelers. 

 The power of this muscle is so great, that it has been 

 ascertained to exert a force equal to twenty pounds, and 

 in consequence the operation for cataract is rendered nearly 

 impossible. It will thus be seen that these muscles are 

 admirable substitutes for the want of hands, in protecting 

 the eyes against the intrusion of things that would injure 

 them. They are also partially separated into four divisions, 

 and by this means assist the straight muscles in turning 



the eye. 



These muscles perform another important office in altering 

 the focus of the eve to accommode itself to the examination 

 of distant or near objects. (See c and h, fig. 5.) The 

 straight and retractor muscles draw back the eye, and 

 forces it upon the substance, and thus in a sliglit degree 

 flattens it, brings it nearer the retina or mirror, and adapts 

 the eye to the observation of distant objects. 



But as these muscles are chiefly employed in supporting 



