MUSCLES OF THE EYE. 305 



4. Abductor Oculi, (Rectus Externus,) 



Arises from the bony partition between the foramen opticum 

 and foramen lacerum, being the longest from its situation ; 

 and is 



Inserted into the globe opposite to the outer canthus. 



Use. To move the globe outwards. 



The oblique muscles are two : 



Obliquus Superior, seu Trochlearis, 



Arises, like the straight muscles, from the edge of the fora- 

 men opticum at the bottom of the orbit, between the levator 

 and abductor oculi ; from thence, runs straight along the pars 

 plana of the ethmoid bone to the upper part of the orbit, where 

 a cartilaginous trochlea is fixed to the inside of the internal 

 angular process of the os frontis, through which its tendon 

 passes, and runs a little downwards and outwards, enclosed in a 

 loose membranous sheath. 



Inserted by a broad thin tendon, into the tunica sclerotica, 

 about half way between the insertion of the attollens oculi and 

 optic nerve. 



Use. To roll the globe of the eye, and turn the pupil down- 

 wards and outwards, so that the upper side of the globe is 

 turned inwards, and the inferior part to the outside of the 

 orbit, and the whole globe drawn forwards towards the inner 

 canthus. 



2. Obliquus Inferior, 



Arises, by a narrow beginning, from the outer edge of the 

 orbitar process of the superior maxillary bone, near its juncture 

 with the os unguis ; and running obliquely outwards, is 



Inserted into the sclerotica, in the space between the abductor 

 and optic nerve, by a broad and thin tendon. 



Use. To draw the globe of the eye forwards, inwards, and 



downwards ; and, contrary to the superior, to turn the pupil 



upwards towards the inner extremity of the eyebrow ; at the 



same time, that the external part of the globe is turned towards 



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