216 PHYSIOLOGY. 



Fig. 20 



Side view of the muscles of the eye in their natural positions, a. b. 

 c. d. the four straight muscles, a. is turned up to prevent the others 

 from being hidden, e. the superior oblique muscle, f. the optic nerve. 

 The other oblique muscle is not shown, but it lies on the other side of 

 the ball, and comes round, and is inserted near the superior oblique ; so 

 that they pull opposite ways, like two men sawing timber. By the com- 

 bined action of all these muscles, an infinite variety of motions of the 

 eye can be produced. 



40. In order to facilitate the motions of the eye it is 

 lodged securely on a soft bed of fat. This is contained in 

 very large cells at the bottom of the orbits, and is more 

 fluid than fat in general, and is less affected than any other 

 part of the body by those causes, which produce general 

 emaciation. The eye-ball may therefore be said to move in 

 a fluid medium, fully adequate to give every necessary sup- 

 port, and at the same time affording the least possible resist- 

 ance. 



41. Defences and Appendages of the Eye. These are 



