142 



PRACTICAL ANATOMY. 



internal and external angular processes of the frontal bone. (Fig. 96.) Carefully 

 remove the bone without injuring the periosteum of the orbit. 



2. Cut through the orbital periosteum and find, immediately under the peri- 

 osteum, the frontal nerve. The frontal nerve lies on the levator palpebrae with the 

 supraorbital artery and vein. It is a branch of the ophthalmic part of the fifth 



Internal rectus muscle 



Superior oblique muscle 



Trochlea 



Levator palpebrse superioris 

 muscle, cut 



External rectus muscle 



Inferior oblique muscle 

 Superior rectus muscle 



Levator palpebrae superior-is 

 muscle, cut 



FIG. 96. VIEW OF LEFT ORBIT FROM ABOVE, SHOWING THE OCULAR MUSCLES 

 (From Hirschfeld and Leveille. ) 



FIG. 97. MUSCLES OF THE EYE. 

 I. Tendon of Zinn. 2. External rectus divided. 3. Internal rectus. 4. Inferior rectus. 5- Superior 

 rectus. 6. Superior oblique. 7. Pulley for superior oblique. 8. Inferior oblique. 9. Levator 

 palpebne superioris. 10, 10. Its anterior expansion. II. Optic nerve. 



nerve. You will see it divide into two branches: (i) the supratrochlear and 

 (2) the supraorbital. The supratrochlear inosculates with the infratrochlear 

 branch of the nasal nerve. The supraorbital comes through the supraorbital 

 foramen, and is distributed to the forehead and inner part of the upper eyelid. 



The levator palpebrae superioris muscle (Fig. 97) lies under the preceding 

 frontal nerve. It is inserted into the tarsal ligament of the upper lid. It lies orv 



