THE HEAD AND NECK. 



143 



the superior rectus muscle. Cut the muscle in the middle, turn the ends out of 

 the way, and expose the superior rectus muscle. (Fig. 96.) 



The Superior Rectus Muscle (Fig. 96). This muscle lies under the levator 

 palpebrae. It is inserted into the sclerotic coat of the eyeball. Cut it, and 

 turn the ends aside. You will see under this muscle a bed of fat. In the 

 centre of the bed of fat and connective tissue is the optic nerve. (Fig. 103.) 



The Optic Nerve. To the outer side of this nerve you will see the external 

 rectus muscle. Between the nerve and this muscle you will see the ciliary ganglion. 



Study the ciliary ganglion according to this outline (Fig. 98) : 



1. Location between the optic nerve and external rectus muscle. 



2. Size, about as large as a pin's head, but spider-like. 



3. Roots : (i) A motor, from the branch of the third nerve to the inferior 

 oblique; (2) a sensory, from the nasal nerve; (3) a sympathetic, from the 

 cavernous plexus. 



4. Distribution and function. Branches are given off from this ganglion, 

 called the short ciliary nerves. They go with the optic nerve surrounding the 



LENTICULAR GANGLION 

 SUPERIOR DIVISION OF THE THIRD NERVE 



NASAL H RANCH OF OPHTHALMIC 



SUPRAORKITAL 

 NER VE 



SHORT CILIARY 

 NER VES 



BRANCH OF THIRD TO 

 INFER [OR OBLIQUE 



LONG ROOT OF LENTICU- 

 LAR GANGLION 



4 



OPTIC NER VE 



THIRD NERVE 

 SIXTH NERVE 

 GASSERIAN GANGLION 



OPHTHALMIC DIVISION 

 OF FIFTH NERVE 



SHORT ROOT OF SYMPA THETIC ROOT OF LENTICULAR 



LENTICULAR GANGLION GANGLION 



FIG. 98. NERVES OF THE ORBIT, FROM THE OUTER SIDE. 

 (From Sappey, after Hirschfeld and Leveille.) 



same. On piercing the sclerotic coat they are joined by the long ciliary 

 branches from the nasal nerve. (Fig. 98.) These branches are distributed to 

 the iris and ciliary muscle. 



From wliat source does the ciliary ganglion derive its sympathetic influence, and 

 hoi*.' docs the same enter the orbit ? 



It derives it from the superior cervical ganglion. The ascending fibres enter 

 the cranium on the internal carotid artery. Here some fibres accompany the 

 branches of this artery to the brain. Other fibres leave the artery in its cavern- 

 ous stage, pass through the sphenoidal fissure to the orbit, and supply the ciliary 

 or lenticular ganglion. 



Give the influence of paralysis of tlie third nerve on t/ie iris. 



Since the iris derives its motor influence, through the ciliary ganglion, from 

 the third nerve, loss of power of contraction of the pupil would follow. 



The Optic nerve, you will find, is surrounded by very small nerves and 

 arteries. (Figs. 98 and 103.) The nerves are: (i) Short ciliary, from the 

 ciliary ganglion ; (2) long ciliary, from the nasal nerve. The arteries are ciliary, 

 derived from the ophthalmic or some of its branches. The optic nerve derives 

 its sheath from the dura mater. 



