204 MANUAL OF MODERN FARRIERY. 



the weight of the eye, they might not have power to turn it 

 so quickly and to such an extent as the animal might wish 

 or require ; therefore the eye is furnished with two other 

 muscles, whose entire office is to turn it. They are placed 

 obliquely, and in consequence are called the oblique muscles. 

 The upper one, a h, is curiously constructed. It emanates 

 from the back part of the orbit, and follows a direction 

 upwards, and towards the inner side, and there, immediately 

 under the ridge of the orbit, it passes through a perfect 

 mechanical pulley, and turning round takes a direction 

 across the eye, and is inserted a little beyond the middle of 

 the eye, and towards the outer side. Thus the globe of the 

 eye is evidently directed inward and upward. This is not 

 all which is accomplished by this remarkable mechanism. 

 That the eye may be completely defended, it is sunk deep 

 in the orbit, but it may be occasionally requisite to bring 

 the eye forward and enlarge the field of vision. Under the 

 influence of fear the eye is positively protruded, and it is 

 not only forced more forward, but the lids are opened more 

 widely. It may be asked, how can this be possibly accom- 

 plished '? The remarkable puUy-muscie, or trochlearis, at 

 h c, readily efiects this, while the straight muscles at the 

 same time do not oppose it, or only regulate the direction 

 of the eye, it is really brought forward. The lower oblique 

 muscle has its insertion just within the lachrymal-bone, n, 

 and proceeding across the eye is fixed into part of the 

 sclerotica, opposite to the other oblique muscle, and turns 

 the eye in an opposite direction, and also assisting the 

 upper oblique muscle in bringing the eye forward from its 

 socket. 



There is another beautiful provision preventing impurities 

 or insects from being carried to and lodging in the corner 

 of the eye, which would, if allowed to accumulate at the 



