THE CEREBRO-SPINAL SYSTEM OP NERVES. 583 



really supplies the fibers to the lingual nerve that are concerned 

 with taste. 



It will thus be seen that the facial nerve has a great variety 

 of important functions, and that paralysis may be more or less 

 serious, according to the number of fibers involved. 



The Trigeminus, Trifacial, or Fifth Nerve.— This nerve has 

 very extensive functions. It is the sensory nerve of the face : 

 but, as will be seen, it is peculiar, being a combination of the 

 motor and sensory ; or, in other words, has paths for both 

 afferent and efferent impulses. The motor and less extensive 

 division arises from a nucleus in the floor of the fourth ventricle. 

 The sensory, much the larger, seems to have a very wide origin. 

 The nerve-fibers may be traced from the pons Varolii through 

 the medulla oblongata to the lower boundary of the olivary body 

 and to the posterior horn of the spinal cord. This origin sug- 

 gests a resemblance to a spinal nerve, the motor root corre- 

 sponding to the anterior, and the sensory to a posterior root, 

 the more so as there is a large ganglion connected with the 

 sensory part of the nerve within the brain-case. 



Efferent Fibers. — 1. Motor. — To certain muscles (1) of mas- 

 tication — ^temporal, masseter, pterygoid, mylohyoid, and the 

 anterior part of the digastric. 3. Secretory. — To the lachrymal 

 gland of the ophthalmic division of this nerve. 3. Vaso-motor. 

 — Probably to the ocular vessels, those of the mucous mem- 

 brane of the cheek and gums, etc, 4. Trophic. — From the re- 

 sults ensuing on section of this nei^e, it has been maintained 

 that special trophic fibers pass in it. We have discussed this 

 subject in an earlier chapter. 



Afferent Fibers. — 1. Sensory. — To the entire face. To par- 

 ticularize regions : 1. The whole of the skin of the face and 

 that of the anterior surface of the external ear. 2. The external 

 auditory meatus. 3. The mucous lining of the cheeks, the floor 

 of the mouth, and the anterior region of the tongue. 4. The 

 teeth and periosteum of the jaws. 5. The lining membrane of 

 the entire nasal cavity. 6. The conjunctiva, globe of the eye, 

 and orbit. 7. The dura mater throughout. 



Many of these afferent fibers are, of course, intimately con- 

 cerned with reflexes, as sneezing, winking, etc. Certain secre- 

 tory acts are often excited through this nerve, as lachrymation, 

 when the nasal mucous membrane is stimulated ; indeed, the 

 paths for afferent impulses giving rise to reflexes, including 

 secretion, are very numerous. 



