SENSE OF SIGHT. 873 



Movements of the Eye.— The position of the eyeball in the orbit 



Fig. 395.— Diagram illustrating Imperfect Perception op Size. (Stirling ) 



corresponds to a ball-and-socket joint, and each eyeball is capable of 

 moving around an immovable centre of rotation, which has been found to be 



Fig. 396.— Diagram illustrating Radial Movement. (Stirling.) 



placed a short distance behind the centre of the eye. The movements of 

 the eye are accomplished by six muscles — four straight and two oblique. 



