CEANIAL NERVES. 205 



pons Varolii. They resemble the spinal nerves, in consisting 

 each of a motor and sensory root; and in the sensory, which 

 is much the larger, having a ganglion on it. The sensory 

 part separates into three divisions, and supplies the scalp in 

 front of the ear, and all the face, as well as the teeth and a 

 large part of the tongue, with sensation; the motor part 

 mixes with the third division of the sensory, and is distri- 

 buted to the muscles of mastication. 



The seventh pair consists of two portions, which emerge 

 on the surface of the brain, in the angle between the crus 

 cerebri, the cerebellum, and the medulla oblongata, and enter 

 the temporal bone together. One portion, the portio mollis 

 or auditory nerve, is the nerve of hearing, and is distributed 

 within the bone; the other, the portio dura or facial nerve, 

 is conducted through the temporal bone, and proceeds to the 

 face to supply the muscles of expression. Within the tem- 

 poral bone, the portio dura gives off the chorda tympani, 

 which traverses the tympanic cavity, and joining with the 

 lingual branch of the fifth nerve passes to a small ganglion, 

 the submaxillary ganglion, and is the nerve alluded to at 

 p. 64 as governing the secretion of the submaxillary gland. 



The eighth pair comprises three pairs of trunks, which arise 

 from the medulla oblongata, and leave the skull by one pair 

 of apertures. (1.) The glossopharyngeal nerves supply sensory 

 branches, devoted to the sense of taste, to the back of the 

 tongue, and motor and sensory branches to the pharynx. 

 (2.) The pneumogastric or vagus nerve is both sensory and 

 motor; it descends on the oesophagus to the stomach, and 

 filaments may be traced from it even to the viscera. It 

 supplies, in its course, branches to the pharynx, larynx 

 and lungs, and the heart, and is intimately associated with 

 the sympathetic, in connection with which it will be again 

 referred to. (3.) The spinal accessory is entirely motor, and 

 consists of two parts, of which one, the accessory, joins the 

 pneumogastric, while the other is distributed to two large 

 muscles, the sterno-mastoid and trapezius. 



The ninth pair, or hypoglossal nerves, are the motor nerves 

 of the tongue. They emerge from the medulla oblongata 

 behind the olivary eminences, which separate them from the 

 eighth pair in front of these eminences. 



