IGO 



THE SENSORIAL FU>X'TIOX. 



or Yoluntaril}- protruded to defend the eye from the action of light, and 

 cannot return, they mistake it for some injurious excrescence or tumour, 

 and proceed to cut it out. The ' katv in the eye ' is a disease well known 

 to the majority of grooms, and this sad remedy for it is deemed the only 

 cure. It is a barbarous practice, and if they were compelled to walk half 

 a dozen miles in a thick dust, without being permitted to vn-pe or to cleanse 

 the eye, they would feel the torture to which they doom this noble animal. 

 A little patience having been exercised, and a few cooling applications 

 inade to the eye while the inflammation lasted, and afterwards some mild 

 astrmgent ones, and other proper means being employed, the tumour 

 would* have disappeared, the haw would have returned to its place, and 

 the animal would have discharged the duties required of him without 

 inconvenience to himself, instead of the agony to which an unguarded and 

 unprotected eye must now expose him. 



The loss of blood occasioned by the excision of the haw may frequently 

 relieve the inflammation of the eye ; and the evident amendment which 

 follows induces these wise men to believe that they have performed an 

 excellent operation ; but the same loss of blood by scarification of the over- 

 loaded vessels of the conjunctiva, would be equally beneficial, and the animal 

 would not be deprived of an instrument of admirable use to him. ^ 



The eye is of a globular figure, yet not a perfect globe. It is rather 

 composed of parts of two globes ; the half of one of them smaller and 

 transparent in front, and of the other larger, and the coat of it opaque, 

 behind. We shall most conveniently begin with the coats of the eye. 



e 



k.. 



A B a supposed object viewed liy the animal, and an inverted image of whicli, a, h, is 



thrown on the retina at the back of the eye. 

 d e The rays proceeding from the extremities of the object to the eye. 

 c c The points where the rays, having passed the cornea and lens, converge by the 



refractive power of the lens. 

 /■ The cornea, or horny and transparent part of the eye, covered by the conjunctiva, 



uniting different parts togetlier. 

 g ' The crystalline (crystal or glassy) lens, behind the pupil, and m front of the vitreous 



humour. 

 h h Muscles of the eye. 

 i The optic nerve, or nerve of sight. 



k The sclerotica (hard firm coat) covering the whole of the eye except tlie portion 

 occupied by the cornea, and being a seeming prolongation of the covering of the 

 optic nerve. 

 I The choroides (receptacle or covering), or choroid coat, covered with a black secretion 



or paint. 



')ii m The iris or rainbow-coloured circular membrane under the cornea, in front of the 



eye, and on which the colour of the eye depends. The duplicature behind is the 



uvea, from being coloured like a grape. The opening in the centre is the pupil. 



n n The ciliary (hair-like) processes. 



o The return, or net-like expansion of the optic nerve, spread over the whole of the 



choroides as far as the lens. 

 «p The vitreous (glass-like) humour filling tlie whole of the cavity of the eye behind 



the lens. 

 The aqueous (water-like) humour filling tlie space between the cornea and the lens. 



