TRIFACIAL NERVE. 



565 



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 3 

 in the petrous portion of the tem- 

 poral bone, on the internal portion 

 of its anterior face. 



The Gasserian ganglion is semi- 

 lunar in form, with its concavity 

 looking upward and inward. At 

 the ganglion the nerve receives 

 filaments of communication from 

 the carotid plexus of the sym- 

 pathetic. This anatomical point 

 is of importance in view of 

 some of the remote effects which 

 follow division of the fifth nerve 

 through the ganglion in .living 

 animals. 



At the ganglion of Gasser, 

 from its anterior and external por- 

 tion, are given off a few small and unimportant branches to the dura mater 

 and the tentorium. 



From the convex border of the ganglion the three great divisions, or 

 branches arise, which have given to the nerve the name of trifacial or tri- 

 geminal. These are : 1, the ophthalmic ; 2, the superior maxillary ; 3, the 

 inferior maxillary. The ophthalmic and superior maxillary branches are 

 derived entirely from the sensory root. The inferior maxillary branch joins 

 with the motor root and forms a mixed nerve. 



The ophthalmic branch, the first division of the fifth, is the smallest of 

 the three. Before it enters the orbit it receives filaments of communication 

 from the sympathetic, sends small branches to all of the motor nerves of the 

 eyeball and gives off a small recurrent branch which passes between the 

 layers of the tentorium. 



Just before the ophthalmic branch enters the orbit by the sphenoidal fis- 

 sure it divides into three branches, the lachrymal, frontal and nasal. 



The lachrymal, the smallest of the three, sends a branch to the orbital 

 branch of the superior maxillary nerve, passes through the lachrymal gland, 



FIG. 210. 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, supratro- 

 chlear ; 8, nasal branch ; 9, external nasal ; 10, in- 

 ternal nasal ; 11, anterior deep temporal nerve ; 

 12, middle deep temporal nerve ; 13, posterior deep 

 temporal nerve; 14. origin of the superficial tempo- 

 ral nerve; 15. great superficial petrous nerve. 



I to XII, roots of the cranial nerves. 



