OF FARRIERY. 



83 



a more complicated nature than in the Horse, 

 consequently, it is very frequently subject to 

 disease by becoming obstructed, and occasion- 

 ing a serious, troublesome complaint ; in the 

 Horse it very seldom occurs, and then but 

 with trifling inconvenience. The action of 

 the haw takes place from any cause that 

 arises from tenderness and pain or inflamma- 

 tion ; and this may be continued so long, 

 that the retractor and adductor muscles per- 

 manently contract, the haw being completely 

 powerless of itself, is left protruded out : 

 when this should be the case, there is no 

 diflliculty or danger in cutting it out with a 

 pair of scissors. 



THE CORNEA. 



In the Horse there is no opaque cornea 

 visible, whilst in man, it constitutes a promi- 

 nent feature of the eye ; which, though it does 

 not appear to add to perfectness of vision, adds 

 greatly to the beauty and expression of the 

 eye ; and as it was not necessary we should 

 see in the night, being supplied with sense 

 and hands to secure sustenance in the day, 

 and requiring much sleep from the activity of 

 the brain, this defect in sight is fully counter- 

 balanced by beauty and expression. 



The transparent cornea is more or less con- 

 vex in all animals, both from its form and the 

 fluid it contains. In Horses, it is not circular 

 but horizontally oblong, being more contracted 

 at the outer than the inner part ; also, the 

 ball of the eye being denser and transparent, 

 that law of optics takes place, that rays of 

 light, passing through a tran-^parent convex 

 body, become bent, conveying objects to a 

 focus, end this focus conveys it to the retina, 

 thus constituting vision. In man, the cornea 

 is often too convex, m consequence of which, 



the rays of light are brought to a focus before 

 they reach the retina; this constitutino- near- 

 sightedness ; the reverse taking place with old 

 people, the cornea being too flat. We cannot 

 so well judge of defect in the sight of the 

 Horse ; there is no doubt that many Horses 

 with prominent eyes, and very convex, have 

 imperfect vision, as they invariably are very 

 apt to shy and start. 



THE IRIS. 



[n examining the eye, and looking into the 

 anterior chamber, which contains the aqueous 

 humour, we there see the iris, and the centre 

 of the iris is that opening called the pupil; 

 looking steadily at it, there is a blueness ap- 

 parent, showing that there is free access to 

 the back part of the eye through the pupil, 

 also showing the iris divides the humours of tl>e 

 eye into two spaces, which are called cham- 

 bers, the anterior and the posterior. The iris 

 appears to hang as a curtain between the 

 cornea and the crystalline lens. The iris 

 is composed of two orders of muscular fibres, 

 and also demonstrates the colour of the eye ; 

 as, for instance, a black iris constitutes a black 

 eye, a blue iris, a blue eye. In bay Horses 

 it is of a cinnamon colour ; sometimes it is 

 white, constituting a wall eye, and with a 

 wall eye there are generally white hairs on 

 the eye-lashes and orbit : the colour of the 

 outer part of the iris is no criterion for the 

 posterior, M'hich is generally black, and is the 

 part that is of service to the Horse's vision. 

 The shape of the iris, at the circumference, is 

 oblong, like the transparent cornea ; it is very 

 muscular, and its fibres are radiated, these being: 

 wound round the circumference with another 

 order of muscular fibres and another round 

 the inner margin, and the union between 



