782 



THE EYE AND VISION. 



[CH. LV. 



Direction of movement. 



Inwards .... 

 Outwards .... 



Upwards .... 

 Downwards 

 Inwards and upwards 

 Inwards and downwards 

 Outwards and upwards . 

 Outwards and downwards . 



By what muscles accomplished 



Internal rectus. 



External rectus. 

 / Superior rectus. 

 ^ Inferior oblique. 

 / Inferior rectus. 

 \ Superior oblique. 



{Internal and superior rectus. 

 Inferior oblique. 

 / Internal and inferior rectus. 

 ( Superior oblique. 

 / External and superior rectus. 

 \ Inferior oblique. 

 ( External and inferior rectus. 

 \ Superior oblique. 



These muscles are all supplied by the third nerve except 

 the superior oblique which is supplied by the fourth and the 

 external rectus by the sixth nerve. The internal rectus is in 



Fig- 593. -Diagram of the axes of rotation to the eye. The thin lines indicate axes of 

 rotation, the thick the position of muscular attachment. 



part supplied by the sixth nerve of the opposite side, via the 

 posterior longitudinal bundle. 



The muscles of the two eyes act simultaneously, so that images 

 of the objects looked at may fall on corresponding points of the 

 two retinae. The inner side of one retina corresponds to the 

 outer side of the other, so that any movement of one eye inwards 



