NERVE OF MASTICATION. 141 



rapidly. The posterior fibres pass to the median line, and 

 Yulpian has seen certain of these decussate with fibres from 

 the opposite side. The anterior fibres pass toward the aque- 

 duct of Sylvius and are lost. The fibres become changed in 

 their character when they are followed inward beyond the 

 anterior wall of the fourth ventricle. Here they lose their 

 white color, become gray, and present numerous globules of 

 gray substance between their filaments. 1 



From the origin above described, the small root passes , 

 beneath the ganglion of Gasser, from w^hich it sometimes, 

 though not constantly, receives a filament of communication, 

 lies behind the inferior maxillary branch of the large root, 

 and passes out of the cranial cavity by the foramen ovale. 

 Within the cranium, the two roots are distinct ; but after the 

 small root passes through the foramen, it is united by a mu- 

 tual interlacement of fibres with the sensitive branch. 9 



The course of the motor root of the fifth possesses little 

 physiological interest. It is sufficient in this connection to 

 note that the inferior maxillary nerve, made up of the motor 

 root and the inferior maxillary branch of the sensitive root, 

 just after it passes out by the foramen ovale, divides into 

 two .branches, anterior and posterior. The anterior branch, 

 which is the smaller, is composed almost entirely of motor 

 filaments, and is distributed to the muscles of mastication. 

 It gives off five branches. The first of these passes to be 

 distributed to the masseter muscle, in its course occasionally 

 giving off a small branch to the temporal muscle and a fila- 

 ment to the articulation of the inferior maxillary with the 

 temporal bone. The two deep temporal branches are dis- 

 tributed to the temporal muscle. The buccal branch sends 

 filaments to the external pterygoid and to the temporal 

 muscle, and a small branch is distributed to the inter- 

 nal pterygoid muscle. From the posterior branch, which 



1 YULPIAN, Essai sur Torigine de plusieurs paires des nerfs craniens, Thfee, 

 Paris, 1853, p. 21. 



2 SAPPEY, Traite cTanatomie descriptive, Paris, 1852, tome ii., p. 233. 



