6U THE EYt.. 



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

 without friction, and by a sheath of considerable density aild 

 firmness, and especially where it is most needed, on the external 

 and superior portions. 



In fi:ont, the eye is supported and covered by the lids, which 

 closing rapidly, protect it from many an injury that threatens 

 and supply it with that moisture which is necessary to preserva 

 its transparency. 



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

 neither origin nor insertion, is a muscle called the orbicularis, oi 

 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 of being closed ; and they 

 are kept open by the energy of the muscles whose office it ""is to 

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

 cles oease 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-brows, and the eye-lashes are peculiarly 

 arranged to guard against the ingress of too much light, or of 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 within 

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

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

 wards. It is concave within, exactly to suit the globe of the eye; 

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

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

 sharp edge. At the wiU 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 gpeedUy 

 dra^vn back, the dust or insect is wiped away as the cartilage 

 agaui passes under the comer of the eye. 



The haw has no muscle attached to it to thrust it forward or 

 draw it dack. When that powerful muscle which the horse 

 possesses in common with other quadrupeds, for the purpose of 

 drawing back the eye, or causing it to recede into its socket, when 

 threatened with danger, is brought into action, the eye presses 

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

 matter is peculiarly accumulated about the inner comer of the 

 eye, it is forced outward in that dirmtion and drives the haw be- 

 ' >re it. Being pressed 1 itween the eye and a polished bone, it 



