Nerves of common sensation 



THE THIRD NERVE OR MOTOR OCULI 



f Olfactory, optic, auditory, parts of 



Nerves of special sense < the facial, glosso-pharyngeal, and of 



(^ the trigeminal. 



{The greater portion of the trigeminal, 

 and part of the facial. 



( The motor oculi, trochlearis, lesser di- 

 Nerves of motion -< vision of the tri-geminal, abducens, 



(^ hypoglossal, and spinal accessory. 

 Mixed nerves Facial, glosso-pharyngeal, and vagus. 



The physiology of the first, second, and eighth nerves will be considered 

 with the Organs of Special Sense, see also figure 416. 



The Third Nerve or Motor Oculi. Origin. The third nerve arises in 



FIG. 408. Section through Superior Corpus Quadrigemmum and Part of the Thal- 

 amus. s, Aqueduct of Sylvius; gr, gray matter of the aqueduct, c.q. s., superior corpus 

 quadrigeminum; /, stratum lemnisci; o, stratum opticum, c, stratum cinereum; Th, pulvinar 

 of optic thalamus; c.g.e, c.g.i, lateral and median corpora geniculata; br.s, br.i, superior and 

 inferior brachia'/, fillet; p.l, posterior longitudinal bundle; r, raphe; ///, third nerve, and 

 n.III, its nucleus; l.p.p, posterior perforated space; s.n, substantia nigra above this is the 

 tegmentum with the circular area of the red nucleus; cr, crusta; II, optic tract; M, medullary 

 center of hemisphere; n.c, nucleus caudatus; st, stria terminalis. (After Quain, from 

 Meynert.) 



three distinct bands of fibers from the gray nuclei surrounding the aqueduct 

 of Sylvius near the middle line, but ventral to the canal, figure 408. The 

 nucleus of origin consists of large multipolar ganglion cells, and extends to 

 the back part of the third ventricle as far as the level of the superior cor- 

 pora quadrigemina. The fibers pass from their origin partly through the 

 red nucleus to their superficial origin in front of the pons at the median side 

 of each crus. The third nerve does not decussate. 



Function. The third nerve supplies the levator palpebrae superioris mus- 

 cle, and all of the muscles of the eyeball, except the superior oblique, to 

 which the fourth nerve is distributed, and the rectus externus which re- 

 ceives the sixth nerve. Through the medium of the ophthalmic or lenticular 



