EXTERNAL STRUCTURE. 85 



rapidly, protoct it from many an injury that tlircatens ;— supply it witi? 

 that moisture which is necessary to preserve its transparency ; in tne 

 momentary act of closing, they give a certain and sufficient respite to a del- 

 icate organ, which would otherwise be fatigued and worn out, by the con- 

 stant glare of day ; when the eye labours under inflammation, defend it from 

 the stimulus of light; and, gradually drooping, permit the animal to enjoy 

 that repose which nature requires. 



Extending round both lids, and, it may be almost said, having neither 

 origin nor insertion, is a muscle called the orbicularis, or circular muscle. 

 Its office is to close the lids in the act of winking or otherwise, but only 

 while the animal is awake. "When he sleeps, this is elTected by another and 

 very ingenious mechanism, for no voluntary muscle will continue in action 

 during sleep. The natural state of the eyelids is tiiatof 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 muscles cease to act, 

 and the lids close by the inherent elasticity of the membrane of which they 

 are composed. 



Tlie skin of the lid is, like that of the ear, exceedingly fine, to prevent 

 unnecessary weight and pressure on such a part, and to give more easy and 

 extensive motion. The lids close accurately when drawn over the eye, and 

 this is effected by a little strip of cartilage, at the edge of each of them, 

 which may be easily felt with the finger, and which preserves them in a 

 hoop-like form, and adapts them closely to the eye and to each other. The 

 lower cartilage, however, does not, as a moment's observation will show, 

 present towaixls the inner corner of the eye, the whole of its flat surface to 

 the upper, but it evidently slopes inward, and only the outer edge of the 

 under lid touches the upper, and, by this means, a little gutter is formed, by 

 which the superfluous moisture of the eye flows to the inner corner, where 

 there is a canal to convey it away, and therefore it neither accumulates in 

 the eye, nor unpleasantly runs down the cheek. 



Along the edges of the lids are placed numerous little hollows, which 

 can be plainly distinguished even in the living horse by slightly turning 

 down the lid. These are the openings into numerous small cells, containing 

 a thick and unctuous fluid, by means of which the eyes are more accu- 

 ralely closed, and the edges of the lids defended from the acrimony of the 

 tears. 



The horse has no eyehrotvs, and the eye/ashes are very peculiarly ar. 

 ranged. The rows of liair are longest and most numerous on the upper lid, 

 and especially towards the outer or temporal corner, because the light 

 comes from above ; and, as the animal stands, and particularly when he is 

 grazing, and from the lateral situation of his eyes, the greater portion of the 

 light, and the attacks of insects, and the rolling down of moisture, would 

 ciiiefly be from the outside or temples. Towards the inner corner of 

 the eye there is little or no eyelash, because there is no probable danger or 

 nuisance in that direction. Only a small quantity of light can enter from 

 below, and therefore the lashes are thin and short ; but as, in the act of 

 grazing, insects may more readily climb up and be troublesome to the eye, 

 towards the inner angle, there the principal or only hair is found on the 

 lower lid. These apparently trifling circumstances will not be overlocked 

 by the careful observer. 



They who are unacquainted with the absurdities of stable management, 

 or who have not carefully examined the abuses which may exist in their 

 own establishments, can scarcely conceive the foolish and cruel practices 

 of some carters and grooms. We know that when the groom is anxious 



