ANATOMY IN A NUTSHELL. 



393 



an anterior or motor, and a posterior or sensory root with a ganglion upon it. 

 It is called the trifacial or trigeminus, lis superficial origin is on the 

 side of the pons, nearer the upper than the lower border. Its motor fibers, 

 which are three or four bundles, are separated from the sensory fibers, which 

 are seventy to one hundred bundles, by a few transverse fibers. The deep 

 origin is in the floor of the fourth ventricle. Its sensory portion is in a nucleus 

 in the pons just below the floor and just beyond the margin of the upper half 

 of the fourth ventricle. The motor portion is a nucleus internal to the sensory 

 and external to the funiculus teres on the upper half of the floor. (Plates CCXIY- 

 CCXV). 



PLATE CCVTII. 



2ND 



Showing Refraction of Light Through Crystalline Lens. 



It is the sensory nerve to the head and face, and a motor NERVE to the 

 muscles of mastication. Its roots pass through an oval opening in the dura mater 

 near the apex of the petrous portion of the temporal bone. The senBory root 

 is from the Gasserian ganglion, which is situated in Meckel's cave. This cave 

 is a depression near the apex of the anterior surface of the petrous portion of the 

 temporal bone. The anterior or motor root passes under the Gasserian ganglion 

 and is not joined to it but joins the inferior maxillary division of the fifth after 

 it passes through the foramen ovale, thus making this pari of the nerve a coin- 

 pound nerve; in fact it is the only pari of the fifth nerve which is a compound 

 nerve for the other two divisions are purely sensory. This ganglion gives off 

 from its anterior edge three trunks. (1) Ophthalmic, (2) Superior maxillary, and 

 (3) Inferior maxillary. It sends communicating branches to the carotid plexus, 

 tentitorium. cerebellum, and the dura mater of the middle fossa. 



