174 MANUAL OF MODERN FARRIERY 



MUSCLES AND PARTS CONNECTED WITH THE 



EYE. 



PLATE III, Figs. 4 and 5. 



The horse has a very extended field of vision. 

 The eye is provided with seven muscles to move 

 it in all directions ; and that they may act with suffi- 

 cient promptitude and power, no fewer than six 

 nerves are directed to the eye generally, or to parti- 

 cular muscles ; and that it may receive no injury 

 from friction, it rests upon a mass of fatty matter, 

 which also enables it to be turned without much 

 exertion of the muscles. Four of the muscles, a, e, 

 and d, are straight ; these rise from the back of the 

 orbit, and are inserted into the ball of the eye, immedi- 

 ately opposite, and at equal distances from each other. 

 One of these, f, rises to the upper part of the eye, 

 immediately behind the transparent and visible portion 

 of it, the office of which is to raise the eye. When it 

 contracts, the eye must necessarily be drawn upward. 

 Another, a, is inserted immediately opposite, at the 

 bottom of the eye, for the purpose of depressing the 

 eye, or enabling the horse to look downwards. A 

 third, e, is inserted at the outer corner, which turns 

 the eye outward ; and a fourth is inserted at the 

 inner corner for turning the eye inwards. By means 

 of all these the eye can rotate, or be turned in 

 any direction at the will of the animal. Should the 

 animal wish to look upward and outward, then the 

 outer and upper muscles are called into action, and 

 can be modified in any manner at the will of the horse. 

 These muscles perform another duty, namely, keep- 

 ing the eye in its place, for, while grazing, the principal 

 weight of the eye rests upon them ; and to aid them 



