CRANIAL NERVES. 519 



IV. T&& pathetic or trochlear are small nerves emerging 

 dorsally from between the mid- and hind- 

 brain, and supplying the superior oblique 

 muscles of the eye. It is possible that they 

 really belong to V. 



V. The trigemmal, or nerve of the "mouth-cleft," 



arising from the medulla oblongata (as do all 

 that follow), has a (Gasserian) ganglion on its 

 root, and three main branches - - the sensory 

 maxillary, which unites with the inner buccal 

 of VII. ; the motor mandibular, which inner- 

 vates the muscles of the jaws ; and the sensory 

 superficial ophthalmic (or orbitonasal), which 

 runs over the eye to the snout, closely united 

 (inside the same sheath) with a similar branch 

 of VII. 



Parallel to these superficial ophthalmics, internal to 

 and above the inner buccal of VII., there is 

 a ganglionated ophthalmicus profundus, which 

 sends branches to the eyeball, snout, etc., and 

 is referred by some to III., by others to V., and 

 is regarded by others as an independent nerve. 



VI. The abducenS) a slender nerve, arising near the 



mid-ventral line, adjacent to V. and VIII., and 

 hidden beneath the former, supplies the external 

 rectus muscle of the eye. 



VII. The facial, the nerve of the spiracular cleft, 

 supplies all the five groups of ampullae on the 

 head, and has numerous branches. 



I . The ophthalmicus superficialis runs over and past 

 the eye, in intimate association with the similar 

 branch of V., and supplies ampullae on the 

 snout. 



SO., superior oblique muscle; E.. eye ; SR., superior rectus; 

 ER., external rectus; SO. VII., superficial ophthalmic branch 

 of VII. ; SO.V., superficial ophthalmic branch of V. ; OP., oph- 

 thalmicus profundus ; A.C.. auditory capsule ; B.PL, brachial- 

 plexus ; R.F., recurrent facial; C.T., chorda tympani ; F.P., 

 facial proper ; Hy., hyoidean ; Hyomn., hyomandibular ; E.M.. 

 external mandibular ; M.M., mandibular muscle ; Sp., spiracle ; 

 P.sp., prespiracular ; PI., palatine; O.B., outer buccal; Mn., 

 mandibular; MX., maxillary; I.E., inner buccal; L., lateral 

 branch of X. ; Py., pyloric branch ; C.. cardiac branch. 



