TRIFAOIAL. OR TRIGEMINAL NERVE. 



635 



Physiological Anatomy of the Trifacial Nerve. The apparent origin of the large root 

 of the fifth is from the lateral portion of the pons Varolii, posterior and inferior to the 

 origin of the small root, from which it is separated by a few transverse fibres of white 

 substance. The deep origin is far removed from its point of emergence from the encepha- 

 lon. The roots pass entirely through the substance of the pons, from without inward 

 and from before backward, without any connection with the fibres of the pons itself. By 

 this course, it reaches the medulla oblongata, where the roots divide into three bundles. 

 The anterior bundle passes from behind forward, between the anterior fibres of the pons 

 and the cerebellar portion of the restiform bodies, to anastomose with the auditory nerve. 

 The other bundles, which are posterior, pass, the one in the anterior wall of the fourth 

 ventricle to the lateral tract of the medulla oblongata, and the other, becoming grayish 

 in color, to the restiform bodies, from which they may be followed as far as the point 

 of the calamus scriptorius. A few fibres from the two sides decussate at the median line 

 in the anterior wall of the fourth ventricle. From this origin, the large root of the fifth 

 passes obliquely upward and forward to the ganglion of Gasser, which is situated in a 

 depression in the petrous portion of the temporal bone on the internal portion of its ante- 

 rior face. 



FIG. 211. Principal branches of the large root of the 

 fifth nerve. (Eobin.) 



a, ganglion of Gasser ; a-u\ ophthalmic division of 

 the fifth : b, ophthalmic ganglion; c.branch from 

 the ophthalmic division of the fifth to the ophthal- 

 mic ganglion; d, motor ocuii communis; e, ca- 

 rotid ; /, ciliary nerves ; g, cornea and iris ; a-h, 

 superior maxillary division of the fifth ; i, two 

 branches from the superior maxillary division 

 of the fifth to the xpheno-palatine ganglion ; j, 

 deep petrosal nerve ; &, filaments from the motor 

 root of the fifth to the internal muscle of the mal- 

 leus; I, mvso-palatine ganglion; m, otic ganglion; 

 n, small superficial petrosal nerve ; o, branches 

 of the fifth to the submaxiUary ganglion; p, 

 branches to the sublingital aanglion; q. facial 

 nerve ; r, sympathetic ganglion ; s. nerve of mas- 

 tication ; ,' chorda tympani.. joining the lingual 

 branch of the fifth ; u, Yidian nerve ; v, branch 

 from the motor root to the internal pterygoid mus- 

 cle ; w, branch of the fifth to the lachrymal gland ; 

 CB, bend of the facial nerve ; y, middle meningeal ar- 

 tery ; z, filament from the carotid plexus to the 

 ophthalmic ganglion ; (1 and 2 are not in the figure) 

 3, external spheno-palatine filaments ; 4, sptieno- 

 palatine ganglion ; 5. naso-palatine nerve ; 6, ante- 

 rior palatine nerve ; 7, inferior maxillary division 

 of the fifth ; 8, nerve of Jacobson. 



FIG. 212. Ophthalmic division of the fifth. (Hirschfeld.) 



1, ganglion of Gasser ; 2, ophthalmic division of the 

 fifth; 3, lachrymal branch; 4, frontal branch; 5, 

 external frontal ; 6, internal frontal ; 7, supra- 

 trochlear'; B, nasal branch; 9, external nasal; 10, 

 internal nasal; 11. anterior deep temporal nerve; 

 12, middle deep temporal nerve ; 13, posterior deep 

 temporal nerve ; 14, origin of the superficial temporal 

 nerve ; 15, great superficial petrous nerve. 



I to XII, roots of the cranial nerves. 



The Gasserian ganglion is semilunar in form (sometimes it is called the semilunar 

 ganglion), with its concavity looking upward and inward. At the ganglion, the nerve 

 receives filaments of communication from the carotid plexus of the sympathetic. This 



