THE EYE. 187 



eye most requires a shield : the under has a few long hairs, 

 placed below its marginal edge. The horse has no eye- 

 brows ; unless we reckon as such the few straggling long 

 hairs above the eyes. The muscles of the lids are three ; 

 one surrounding the whole orbit, a sphincter, termed 07'bi- 

 cularis, which shuts the eyelids ; the others are termed 

 levator palpehrce superioris, internus and externus. The 

 externus arises from the frontal bone and fascia, and is in- 

 serted into the upper lid, blending with the fibres of the 

 orbicularis. The internus arises from the bottom of the 

 orbit, to be inserted into the upper lid, by a tendon, which 

 becomes very tine and much expanded, as it proceeds for- 

 ward, to be fixed into the margin of the upper eyelid. These 

 muscles, in all their diversified movements, are much assisted 

 by other fascial muscles. The lachrymal gland is a conglo- 

 merate body, lodged within the conjunctiva at the upper and 

 outer part of the orbit ; in a fossa above the external angle, 

 and in immediate connexion with the frontal arch ; its several 

 lobuli, together, send out eleven to thirteen little ducts, 

 which penetrate the conjunctiva, and pour out the saline fluid 

 known as the tears. The lachrymal gland can be stimulated 

 by brutality to a more than an ordinary supply of the tears, 

 which then flow over the cheek : the ordinary supply passes 

 off by an opening termed puncta lachrymalia ; being guided 

 there by a groove formed by the junction of the eyelids, with 

 a protuberant dark-coloured body, situated between the in- 

 ternal angle of the palpebrse, termed caruncula lachrymalia ; 

 which is covered with an intermediate structure, between 

 mucous membrane and true skin. Thus directed, the tears 

 are carried into the lachrymal duct ; and so pass into the 

 nose by the ductus ad nasum. It has been much disputed 

 whether the horse has a lachrymal sac or not. If by a sac 

 is meant a dilatation of the nasal duct, as large in proportion 

 as the human lachrymal sac, then decidedly the horse has 

 none; but if, by the horse having no lachrymal sac, it is 

 meant that the nasal duct in the horse is of one size through- 

 out, then those who make such an assertion are assuredly 

 WTong. The horse has a well-marked enlargement of the 

 duct, where the sac should be ; and this we presume to view 

 as the horse's lachrymal sac. The vessels of the eye are 

 arteries, from the external and internal carotids : the external 



