144 



PRACTICAL ANATOMY. 



The external rectus muscle lies to the outer side of the optic nerve. It is 

 attended by the lachrymal nerve, a branch of the ophthalmic nerve, and the 

 lachrymal artery, a branch of the ophthalmic artery. You will dissect the 

 three together and associate them in your memory. The lachrymal structures 

 are on their way to the lachrymal gland. Turn the external rectus muscle 



Tendon of superior oblique 



Trochlea 



Internal reotue 



Inferior oblique muscle 



Levator palpebrae super- 



ioris, cut 

 Superior rectus 



External rectus 



Inferior rectu* 



FIG. 99. LEFT EYEBALL SEEN IN ITS NORMAL POSITION IN THE ORBIT, WITH VIEW OF THE 

 OCULAR MUSCLES. (After Merkel, modified.) 



FIG. loo. MUSCLES OF ini. \-.\\-.. TENDON OR LK;AMKM OF /INN. 

 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 

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



outward, and on its inner surface you will see the fine filaments of the sixth 

 cranial nerve the abducens. 



The Superior Oblique Muscle and the Fourth Nerve (Fig. 97). These 

 form a group by themselves. You will trace the tendon of this muscle around 

 the trochlea, where it turns at a right angle and passes outward under the 



