504 



HUMAN ANATOMY. 



6. Obliquus Superior (Figs. 514, 516). 



Attachments. — The superior oblique muscle of the eyeball arises a little in 

 front of the inner part of the optic foramen and passes forward along the upper and 

 inner wall of the orbit to terminate in a round tendon which passes through a ten- 

 dinous loop, the trochlea, attached to the fovea trochlearis of the frontal bone. 

 Thence it is reflected outward, downward, and backward, and, passing beneath the 

 superior rectus, is inserted into the sclera beneath the outer margin of that muscle 

 and at about the equator of the eyeball. 



Nerve-Supply. — From the trochlearis or fourth nerve. 



Action. — To rotate the eyeball so that the pupil is directed inward and 

 downward. 



Fig. 516. 



Levator palpebrae superioris — 



Superior oblique 

 Superior rectus 

 Externa! rectus (cut) 



Internal rectus 

 Optic nerve 

 Stump of external rectus 



Trochlea 



Insertion of levator palpebrae 

 superioris into upper tarsal 

 plate 



Inferior oblique 



Inferior rectus 



Lateral view of ocular muscles after removal of outer wall of orbit ; elevator of upper lid has been pulled 



upward and inward. 



7. Obliquus Inferior (Fig. 516). 



Attachments. — The inferior oblique muscle arises near the margin of the 

 orbit from a small depression on the orbital surface of the maxilla. It is directed out- 

 ward, backward, and upward, and, passing between the inferior rectus and the floor 

 of the orbit, is inserted into the sclera a little behind the equator of the eyeball and 

 under cover of the external rectus. 



Nerve-Supply. — From the oculo-motor nerve. 



Action. — To rotate the eyeball so that the pupil is directed upward and outward. 



Fasciae of the Orbit. — The muscles, nerves, and vessels of the orbit are em- 

 bedded in a mass of loose areolar tissue which, abundantly intermingled with a soft 

 fat, completely fills the orbital cavity. Around the vessels, nerves, and muscles this 

 areolar tissue condenses to form their sheaths, and a special condensation, the 

 capsule of Tenoii (fascia bulbi), surrounds the posterior four-fifths of the eyeball, 

 forming a socket for it. The inner surface of this capsule is smooth and is united to 

 the outer surface of the sclera only by lax and slender bands of fibres which traverse 

 a distinct lymph-space termed the space of Tenon (spatium interfasciale), which inter- 

 venes between the capsule and the eyeball, thus facilitating the movements of the 

 latter in the socket. Posteriorly the capsule is continuous with the sheath of the 

 optic nerve and anteriorly it joins with the conjunctiva anterior to the line of insertion 

 of the rectus muscles into the sclera. The tendons of the rectus muscles conse- 

 quently perforate the capsule, which is prolonged backward upon the tendons for a 

 short distance, — in the case of the superior oblique as far as the trochlea. — and then 

 becomes continuous with the areolar sheaths of the muscles which are intnnately 



