EXTERNAL STRUCTURE. S"/ 



vrhivu .ve liave spoken, formed by the sloping of the under lid, towards the 

 cornel of the eye ; and there are two little orifices, that conduct it to a 

 small leservoir within, and at the upper part of the lachrymal bone, (fig i, 

 p. d6). A little protuberance of black or pied colour, called the caruncle, 

 placed in the very corner of the eye, and to be seen without opening the 

 lids, IS situated between these orifices, and guides the fluid into them. 

 From this reservoir the tears are conveyed by a long canal, the lachrymal 

 duct, partly bony and partly membranous, to the lower part of the nose. 

 A little within the nostril, and on the division between the nostrils, is seen 

 the lower opening of this canal ; the situation of which our readers should 

 carefully mark, and bear in mind its real use, for not only horsemen, but 

 even some careless veterinary surgeons, have mistaken it for a glanderous 

 ulcer, and have condemned a useful and valuable animal. It is found just 

 before the skin of the muzzle terminates and the more delicate membrane 

 of the nostril commences. The opening of the canal is placed thus low 

 because the membrane of the nose is exceedingly delicate, and would be 

 irritated and made sore by the frequent or constant running down of the 

 tears. 



This canal is sometimes obstructed in the human being, and the reservoir 

 is distended and bursts ; an ulcer is then formed, very difficult to heal, and 

 only healed by a metal style or pin, penetrating into the duct, being worn 

 for a considerable time. Fortunately the lachrymal duct is rarely obstructed 

 m the horse, for, if it were, and ulceration were to follow, no mechanical 

 contrivance could retain the style or pin in its place. The dog is subject 

 to obstructions of this canal, and the ulcer formed by the bursting of the 

 sac is never healed. 



There is, however, something yet wanting. We have a provision for 

 supplying the eye with requisite moisture, and for washing from off the 

 transparent part of it insects or dust which may annoy the animal. What 

 becomes of these impurities when thus washed off? Are they carried by 

 the tears to the corner of the eye, and so pass down this duct, and irritate 

 and obstruct it ; or do they accumulate at the inner angle of the eye ? 

 There is a beautiful contrivance for disposing of them as fast as they 

 enter the eye. Concealed within the inner corner of the eye, or only 

 the margin of it, black or pied, visible, is a triangular-shaped cartilage, 

 the haw, with its broad part before. It is concave within, exactly to 

 suit the globe of the eye ; and it is convex without, accurately to adapt 

 itself to the membrane lining the lid; and tlie base of it is reduced to a 

 thin or almost sharp edge. At the will of the animal this is suddenly pro- 

 truded from its hiding-place, passes rapidly over the eye, and shovels up 

 every nuisance mixed with the tears, and then, being speedily drawn back, 

 the dust or insect is wiped off as the cartilage again passes under tiie 

 corner of the eye. 



How is this managed ? This cartilage has no muscle attached to it, and 

 the limbs, and the different parts of the body, when put in motion by tlie 

 influence of the will, are moved invariably by muscles. The mechanism 

 is simple and effectual. There is a great mass of fat at the back of tiie pye, 

 that the eye may be easily moved ; and this fat is particularly accumulnted 

 about the inner corner of the eye, and beneath, and at the point of this car- 

 tilage. The eye of the horse has likewise very strong muscles attached 

 to :% and one, peculiar to quadrupeds, of extraordinary power, and by 

 whose aid, if the animal has not hands to ward off a danger that threatens, 

 he is at least enabled to draw the eye back almost out of the reach of tliat 

 danger. 



