THE CRANIAL NERVES. 



537 



Division of the nerve is followed by a relaxation or paralysis of 

 the muscle. In consequence of the now unopposed action of the 

 inferior oblique muscle, the anterior pole of the eyeball is turned 

 upward and inward with slight torsion toward the middle line. The 

 diplopia consequent upon this paralysis is homonymous, the images 

 appearing one above the other. The image of the paralyzed eye is 

 below that of the normal eye and its upper end inclined toward that 

 of the normal eye. 



Function. The function of this nerve is to transmit nerve im- 

 pulses to the superior oblique muscle and to excite it to contraction. 



FIFTH PAIR. THE TRIGEMINAL. 



The fifth cranial nerve, the trigeminal, consists of both afferent and 

 efferent axons which for the most part are separate ana 'ctistinct. 

 'JL'ne afferent axons constitute by far the major portion, the efferent 

 fibers the minor 

 portion, of the 

 nerve. 



Origin of the 

 Afferent Axons. 

 -The afferent 

 axons serve to 

 bring into relation 

 the skin, mucous 

 membranes of the 

 head and face, 

 and other sentient 

 structures, with 

 certain sensor 

 end-nuclei irL-ihe 

 pons, medulla ob- 

 longata, and ad- 

 joining structures. 3 



Iney nave tneir FlG 24 ^ SCHEME or ORIGIN AND CONSTITUTION or THE 

 Ongj^in the mon- TRIGEMINAL NERVE, i. Centrally coursing fibers. 2,3, 



axonic Cells in the 4; Peripherally coursing fibers of the cells of the ganglion 



of Gasser. R, N. Nuclei of origin of the efferent fibers. 

 6. Motor root.A Central terminations of the large root. 



wmcri Tests 



on me apex of the petrous portion of the temporal bone. The cells 

 of this ganglion give origin to a short process which soon divides into 

 two branches, one of which passes centrally, the other peripherally 

 (Fig. 247). The centrally directed branches collectively form the 

 so-called large or sensor root; the peripherally directed branches 

 collectively constitute the three main divisions of the nerve: viz., the 



