THE CRANIAL NERVES. 



533 



eral sympathetic neurons. As the ciliary ganglion receives filaments 

 from the cavernous plexus of the sympathetic and filaments which 

 become a part of the trigeminal nerve, it is probable that the ciliary 

 nerves contain not only motor, but vaso-motor and sensor fibers. 



Properties. Stimulation of the nerve near its exit from the en- 

 cephalon is followed by contraction of the muscles to which it is dis- 

 tributed with the following results, viz. : 



1 . Diminution in the size of the pupil. 



2. Accommodation of the eye for near vision. 



3. Elevation of the upper eyelid. 



4. Internal deviation and rotation upward and inward of the anterior 



pole of the eye, combined with a small amount of torsion toward 



the mesial line, due to 



preponderating action 



of the internal rectus 



and inferior oblique 



muscles. 



Division of the nerve 

 experimentally or compres- 

 sion from a pathologic 

 lesion is followed by a 

 relaxation of the muscles, 

 with the following effects, 

 viz. : 

 i 



FIG. 244. INTRA-ORBITAL PORTION OF THE 

 THIRD NERVE, i. Optic nerve. 2. Third 

 nerve. 3. Superior branch. 4. Inferior 

 branch. 5. Abducens. 6. Trifacial. 7. 

 Ophthalmic branch divided. 8. Nasal 

 branch. 9. Ciliary ganglion. 10. Motor 

 branch to this ganglion from the inferior 

 branch of the third nerve. n. Sensory 

 fibers. 12. Sympathetic fibers. 13. Ciliary 

 nerves . (Sappey .) 



8 7 tO 



Dilatation of the pupil, 

 the iris responding 

 neither to light nor to 

 efforts of accommoda- 

 tion. 



2. Loss of the accommoda- 



tive power. 



3. Falling of the upper eye- 



lid (ptosis). 



4. External deviation and rotation downward and outward of the 



anterior pole of the eyeball combined with a small amount of 

 torsion toward the mesial line due to the unopposed action of 

 external rectus and the superior oblique muscles. 



5. Double vision or diplopia. The image of the eye of the paralyzed 



side is projected to the opposite side of the true image and to 

 the upper part of the visual field. Owing to the slight mesial 

 torsion the false image is inclined away from the true image. 



6. Immobility and slight protrusion of the eyeball. 



Function. The function of the third nerve is to transmit nerve 

 impulses from the nuclei of origin to all the muscles of the eye except 

 the external rectus and superior oblique and excite them to activity. 



