308 ANATOMY AND PHYSIOLOGY 



mandibular nerve is in the infratemporal fossa, and is the nerve of sensation 

 for the lower teeth and structures of the lower jaw. The motor root joins this 

 branch to supply the muscles of mastication. 



The nerve of the sense of taste, called the lingual (or gustatory}, accom- 

 panies the mandibular nerve, from the anterior two-thirds of the tongue. 



Surgical notes. Facial neuralgia is sometimes so severe and intractable 

 that the semilunar ganglion is removed by the surgeon. This interferes with 

 sensation of the face, but not with motion. 



Three sensitive points on the face where three sensory branches of the 

 trifacial pass through foramina are: the supraorbital foramen, for the supra- 



FIG. 198. THE DISTRIBUTION OF THE THREE DIVISIONS OF THE FIFTH NERVE. 



(Leidy.) 



orbital branch of the ophthalmic; the infraorbital foramen for the infra- 

 orbital branch of the maxillary; the mental foramen for the mental branch 

 of the mandibular. Section of these nerves is sometimes done for facial 

 neuralgia. 



The sixth, or abducens, is a motor nerve, supplying the 

 external rectus muscle, which turns the eye outward, or abducts 

 it. 



The seventh, or facial (Fig. 199), is a motor nerve. It passes 

 through the channel in the petrous bone called the facial or 

 Fallopian canal (which brings it close to the middle ear). Emerg- 

 ing from the skull it passes forward through the parotid gland, 

 and divides into many branches supplying all the muscles of 

 expression. 



