SENSE OF SIGHT. 215 



39. Four of the .muscles of the eye are called straight or 

 recti muscles ; the other two are named the oblique muscles. 

 'The first four arise from the back part of the orbit, and are 

 inserted by broad thin tendons into the four sides of the 

 globes near the junction of the cornea with the sclerotic 

 coat. The white pearly appearance of the eye is caused by 

 these tendons. The oblique muscles arise from the front and 

 inner side of the orbit, and pass to the eye-ball at right angles 

 from the straight muscles, one passing over its upper surface, 

 and the other upon its under surface, and both are inserted 

 into its outer side, one a little above its horizontal axis, the 

 other a little below it. The superior oblique muscle is, how- 

 ever, worthy of more particular notice, as no part of the 

 body exhibits clearer marks of design and contrivance. It 

 arises as I have said, from the bottom of the orbit, it proceeds 

 forwards and becomes tendinous, and when it reaches near 

 the margin of the orbit, it passes through a little cartilagi- 

 nous pulley, by which the direction of its action is changed, 

 precisely as we see done by a pulley among the ropes of a 

 ship ; after passing through this little loop, which is dense> 

 smooth, and elastic, and furnished with a lubricating fluid to 

 diminish friction, the tendon runs obliquely backwards and 

 towards the internal angle to be inserted into the ball. When 

 this muscle acts, the eye is rolled directly inwards. Thus 

 the muscle pulls in a direction contrary to its own action, as 

 when a man raises himself by a rope thrown over a beam. 

 The other, or inferior oblique muscle, rolls the eye outwards 

 towards the temple. When they both act together, the eye 

 is steadily carried forwards. The recti muscles move the 

 eye in four directions, upwards, downwards, to the right, and 

 to the left, each movement being affected by its appropriate 

 muscle. When the four act together, the eye is drawn back 

 towards the bottom of the orbit. 



