EXTERNAL STRUCTURE. 85 



rapidly, protect it from many an injury that threatens; — supply it with that 

 moisture which is necessary to preserve its transparency; — in the momen- 

 tary act of closing, they give a certain and sufficient respite to a delicate 

 org'an, which would otherwise be fatigued and worn out, by the constant 

 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 ori- 

 gin 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 effected by another and very inge- 

 nious mechanism, for no voluntary muscle will continue in action during 

 sleep. 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 muscles cease to act, and the 

 lids close by the inherent elasticity of the membrane of which they are com- 

 posed. 



The skin of the Hd is, like that of the ear, exceedingly fine, to prevent 

 vmnecessary 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 

 shew, present towards the inner corner of the eye the whole of its flat sur- 

 face 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 shghtly 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- 

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

 tears. 



The horse has no eyebrows, and the eyelashes are very peculiarly ar- 

 ranged. The rows of hair 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 roUing down of moisture, 

 would chiefly 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 trilling circumstances will not be over- 

 looked 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 estabhshments, can scarcely conceive the foolish and cruel practices 

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



