THE SENSORIAL FUN:'TQN. 



himself, instead of the agony to which an unguarded and unprotecU 1 ye must novt 

 expose him. 



The loss of blood occasioned by the excision of the haw lu.iy frequently relieve the 

 inflammation of the eye ; and the evident amendment which follows induces these 

 mse men to believe that they have performed an excellent operation ; but the same 

 loss of blood by scarification of the overloaded vessels of the conjunctiva would be 

 equally beneficial, and the animal would not be deprived of an instrument of admi 

 table 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. 



A B a supposed object viewed by the animal, and an inverted image of which, a, b, is thrown 



on the retina at the back of the eye. 

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



power of the lens. 



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

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



different parts together. 

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



humour. 



Muscles of the eye. 

 The optic nerve, or nerve of sight. 

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



by the cornea, and being a seeming prolongation of the covering of the optic nerve. 

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



or paint. 

 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. 

 The ciliary (hair-like) processes. 



The retina, or net-like expansion of the optic nerve, spread over the whole o: tlie cho- 

 roides as far as the lens. 

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



lens. 

 q The aqueous (water-like) hu/nour filling the space between the cornea and the lens. 



The conjunctiva, f, is that membrane which lines the lids, and covers the fore part 

 of the eye. It spreads over all that we caji see or feel of the eye, and even its trans- 

 parent part. It is itself transparent, and transmits the colour of the parts beneath. 

 it is very susceptible of inflammation, during which the lining of the lids will become 

 intensely red, and the white of the eye will be first streaked with red vessels, and then 

 covered with a complete mesh of them, and the cornea will become cloudy and 

 opaque. It is the s,eat of various diseases, and, particularly, in it commences that 

 sad inflammation of the horse's eye which bids denance to the veterinary surgeon't 

 nkill and almost ir variably terminates in blindness. 



The examination of the conjunctiva, by turning down the lid, will enable us tc 

 *orm an accurate judgment of the degree of inflammation which exists in the eye. 



Covering Ihe back part of the eye, and indeed four-fifths of the globe of it, is the 



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