THE SENSORIAL FUNCTION. 85 



insects or dust that 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 ano-le 

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

 acccumulate. 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 

 forwards. It is concave within, exactly to suit the globe of the eye; it is convex 

 without, accurately to adapt itself to tiie membrane lining the lid ; and the base of it 

 is reduced to a thin or almost sharp edge. At the will of the animal this is suddenly 

 protruded from its hiding-place. It passes rapidly over the e3'^e, and shovels up every 

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

 insect is -wiped away as the cartilage again passes under the corner of the eye. 



How is this managed \ The cartilage has no muscle attached to it; and the limbs 

 and the dilTerent parts of the body, when put into motion by the influence of the will, 

 are moved invariably by nmscles. The mechanism, however, is simple and effectual. 

 There is a considerable mass of fotty matter at the back of the eye, in order that this 

 organ may bo easily moved ; and this fat is particularly accumulated about the inner 

 corner of the eye, and beneath, and at the point of this cartilage. The eye of the 

 horse has likewise very strong muscles attached to it, and one, peculiar to quadrupeds, 

 of extraordinar}^ power, 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 that danger. 



Dust, or gravel, or insocts, may have entered the eye, and annoy the horse. This 

 muscle suddenly acts : the eye is forcibly drawn back, and presses upon the fatty 

 matter. That may be displaced, but cannot be reduced into less compass. It is 

 forced violently towards the inner corner of the eye, and it drives before it the haw ; 

 and the haw, having likewise some fat about its point, and being placed between the 

 eye and an exceedingly smooth and j)olished bone, and being pressed upon by the 

 eye as it is violently drawn back, shoots out with the rapidity of lightning, and, 

 guided by the eyelids, projects over the eye, and thus carries off the offending matter. 



In what way shall we draw the haw back again without muscular action ? Another 

 principle is called into play, of which mention has already been made, and of which 

 we shall have much to say, — elasticity. It is that principle by which a body yields 

 to a certain force impressed upon it, and returns to its former state as soon as that 

 force is removed. It is that by which the ligament of the neck (p. 75), while it sup- 

 ports the head, enables the horse to graze — by which the heart expands after closing 

 on and propelling forward the blood in its ventricles and the artery contracts on the 

 blood that has distended it, and many of the most important functions of life are 

 influenced or governed. This muscle 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 excrescence 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 w4pe or to cleanse the eye, they would feel the tor- 

 ture 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 

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