CRANIAL CAVITY. 



rounding its posterior two-thirds is pierced by the optic nerve 

 and muscle tendons. [405] 



MUSCLES. 



Levator Palpebrae Superioris (the uppermost). Origin; 

 margin of the foramen. Insertion ; (mainly) upper border of 

 tarsal cartilage; (slightly) Orbicularis palpebrarum, skin of up- 

 per lid, conjunctiva, upper border of orbital margin. [405] 



Recti. All arise from a membranous ring which surrounds 

 the optic foramen and is separable into superior and inferior 

 common tendons; all are inserted in the sclerotic just behind 

 the corneal margin. Superior rectus : Origin; the superior 

 tendon: Insertion; eyeball in its vertical plane just internal 

 to its axis. Inferior rectus: Origin; the inferior tendon: In- 

 sertion, eyeball in its vertical plane. Internal rectus : Origin; 

 the inferior tendon: Insertion; eyeball in its transverse 

 plane. External rectus : Origin; (upper head) the superior 

 tendon; (lower head) the inferior tendon. Insertion; eyeball 

 in its transverse plane. [405] 



Obliquus Superior. Origin; margin of optic foramen be- 

 tween the Recti superior and internus. Course; its narrow 

 tendon runs through a fibrous pulley (trochlea) attached to 

 the roof of the orbit and then bends outward under the Superior 

 rectus tendon. Insertion; sclerotic between the Recti su- 

 perior and externus, midway between the cornea and entrance 

 of the optic nerve. [406] 



Obliquus Inferior. Origin; floor of orbit antero-internally, 

 external to the naso-lachrymal groove. Course; under the 

 Inferior rectus and between the eyeball and the External 

 rectus. Insertion ; sclerotic between the Recti, superior and 

 externus, posterior to the Superior oblique. [406] 



NERVES. 



Ophthalmic. The lachrymal runs through the outer angle 

 of the sphenoidal fissure above the muscles and forward below 



[53] 



