SENSE OF SIGHT. 



559 



and the external rectus, behind the insertion of the superior 

 oblique. Nerve-supply is from the oculomotorius. 



Functions of the Ocular Muscles (Figs. 335, 336). The supe- 

 rior rectus turns the eye upward and inward ; when the eye is 

 turned directly upward this is brought about by the conjoint 



4 4 



6 6 



FIG. 335. Movements of the eyeballs: 1, inferior oblique; 2, superior rectus; 3, 

 external rectus ; 4, internal rectus ; 5, superior oblique ; 6, inferior rectus. 



action of the superior rectus and the inferior oblique. The in- 

 ferior rectus turns the eye downward and inward ; when the eye 

 is turned directly downward, this is effected by the conjoint action 

 of the inferior rectus and the superior oblique. The internal 



FIG. 336. Horizontal section of left eye. Arrows show direction of pull of the 

 muscles. The axis of rotation of the external and internal recti would pass through 

 the intersection of a and at right angles to the plane of the paper (Stewart). 



rectus turns the eye inward ; the external rectus turns it outward. 

 The superior oblique rotates the eye outward on its anteroposterior 

 axis, and corrects the inward deviation of the inferior rectus. The 

 inferior oblique rotates the eyeball outward on its anteroposterior 

 axis, and corrects the inward deviation of the superior rectus. 



