310 PRACTICAL ANATOMY. 



tracts. The optic nerves pass forward through the optic 

 foramina in the lesser wings of the sphenoid, pierce the 

 sclerotic and choroid, and are distributed in the retinae. 



3. MOTOR OCULI NERVE. Origin, from inner side 

 of cms cerebri, just in front of pons. Runs along side 

 of body of sphenoid, passes through the anterior lacer- 

 ated foramen, and is distributed to all the muscles of the 

 orbit, except the external rectus and superior oblique. 

 It furnishes the motor root to the lenticular ganglion, 

 and, through it, animates the sphincter muscle of the iris. 



4. PATHETICUS NERVE. Origin, from the outer side 

 of the cms. It is a small nerve, and passes through the 

 anterior lacerated foramen to the superior oblique 

 muscle. 



5. TRIFACIAL NERVE. Origin, by two roots from 

 the side of pons. A large sensory and a small motor 



root, separated by some of the fibres of the pons. It is 

 the largest cranial nerve. The sensory is the larger 

 root, and is distributed to the structures of the upper, 

 lateral, anterior, and deep parts of the head. The two 

 roots pass forward and outward to the apex of the 

 petrous part of the temporal bone ; here the sensory 

 root enters a large semilunar ganglion, the Casserian, 

 while the motor root passes beneath it. The Casserian 

 ganglion rests directly on the surface of the bone beneath 

 the dura mater. It is semilunar in shape, the convexity 

 being anterior. It sends off three branches, ophthal- 

 mic, superior maxillary, and inferior maxillary. The 

 ophthalmic supplies sensation to the contents of the orbit, 

 to the skin above the orbit and of the nose, and to the 

 mucous membrane of the anterior part of the nasal 

 cavities. It sends off three branches, lachrymal, frontal, 

 and nasal. The lachrymal is distributed to the struct- 

 ures of the orbit. The frontal divides, near the anterior 



