60 THE KYI. 



nous parts of the orbit, upon which the eye may be readily moved 

 without friction and by a sheath of considerable density and 

 firmness, and especially where it is most needed, on tiie exteruai 

 and superior portions. 



In front, the eye is supported and covered by the lids, which 

 closinf? rapidly, protect it Irom many an injury that threatens 

 and supply it witii that moisture which is necessary to preserve 

 its transparency. 



Extending round both lids, and, it may be almost said, having 

 neither origin nor insertion, is a muscle called the orbicidaru, or 

 circular muscle. Its office is to close the lids in the act of wink- 

 ing or otherwise, but only while the animal is awake. When he 

 sleeps, this is effected by another and very ingenious mechanism. 

 The natural state of the eyelids is that ol' being closed ; and they 

 are kept open by the energy of the muscles whose office it is 1o 

 raise the upper lid. As sleep steals upon the animal, these mus- 

 cles cease to act, and the lids close by the inherent elasticity of 

 the membrane of which they are composed. 



The skin of the lid is, like that of the ear, exceedingly fine, in 

 order to prevent unnecessary weight and pressure on such a part* 

 and to give more easy and extensive motion. 



The horse has no eye-brow^, and the eye-lashes are peculiarly 

 arranged to guard against the ingress of too much light, or oi' in- 

 sects, and therefore should never be clipped, as is the custom 

 with some senseless grooms in England. 



There is a beautiful contrivance about the horse's eye, to cleai 

 it of dust, insects, and other foreign matters. Concealed withir 

 its inner corner, or only the margin of it, black or pied, visible 

 is a triangular-shaped cartilage, the haiv^ with its broad part for- 

 ■^ards. It is concave within, exactly to suit the globe of the eye; 

 it is convex without, acurately to adapt itself to the membrane 

 luring the lid ; and the base of it is reduced to a thin or almost 

 sharp edge. At the will of the animal this is suddenly protruded 

 from its hiding-place. It passes rapidly over the eye, and shovels 

 up every nuisance mixed with the tears, and then, being speedily 

 drawii back, the dust or msect is wiped away as the cartilage 

 again passes under the corner of the eye. 



The ha\D has no muscle attached to it to thrust it forward or 

 draw it dack. When that powerful muscle which the horse 

 possesses m common with other quadrupeds, for the purpose of 

 dra\\ang back the eye, or causing it to recede into its socket, when 

 thi'eatened with danger, is brought into action, the eye presses 

 upon the flitty matter below it, and as a portion of that fotty 

 inatter is peculiarly accumulated about the mner corner of the 

 r ye, it is forced outward in that direction and drives the haw be- 

 '■ ire it. Being pressed ^ ^tween the eye and a polished bone, it 



