THE SENSORIAL FUNCTION. 127 



ceases to act, and the eye resumes its natural situation in the orbit. There is 

 room for the fatty matter to return to its place, and it immediately returns by 

 the elasticity of the membrane by which it is covered, and draws after it this 

 cartilage with which it is connected, and whose return is as rapid as was the 

 projection. 



The old farriers strangely misunderstood the nature and design of the haw, 

 and many at the present day do not seem to be much better informed. When, 

 from sympathy with other parts of the eye labouring under inflammation, and 

 becoming itself inflamed and increased in bulk, and the neighbouring parts 

 likewise thickened, it is either forced out of its place, or voluntarily protruded 

 to defend the eye from the action of light and cannot return, they mistake it 

 for some injurious excrescenee or tumour, and proceed to cut it out. The 

 " haw 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 wipe 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 made to the eye while the inflammation lasted, and 

 afterwards some mild astringent 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 opera- 

 tion j 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 admirable use to him. 



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

 posed 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 tbrowr. 



on the retina at the back of the eye. 

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



power of the lens* r 



de 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. 

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



humour. 

 h h Muscles of the eye. 



t The optic nerve, or nerve of sight. . , 



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



