174 THE HUMAN BODY. 



spinal nerves in having two roots; one of these is much 

 larger than the other and possesses a ganglion (the Gasserian 

 ganglion) like the dorsal root of a spinal nerve. Beyond 

 the ganglion the two roots form a common trunk which 

 divides into three main branches. Of these, the ophthalmic 

 is the smallest and is mainly distributed To~the muscles and 

 skin over the forehead and upper eyelid; but also gives 

 branches to the mucous membrane lining the nose,, and to 

 the integument over it. The second division (superior maxil- 

 lary nerve) of the trigeminal gives branches to the skin over 

 the temple, to the cheek between the eyebrow and the angle 

 of the mouth, and to the upper teeth; as well as to the 

 mucous membrane of the nose, pharynx, soft palate and roof 

 of the mouth. The third division (inferior maxillary) is the 

 largest branch of the trigeminal; it receives some fibres from 

 the larger root and all of the smaller. It is distributed to 

 the side of the head and the external ear, the lower lip and 

 lower part of the face, the mucous membrane of the mouth 

 and the anterior two thirds of the tongue, the lower teeth, 

 the salivary glands, and the muscles which move the lower 

 jaw in mastication. 



The sixth pair of cranial nerves (Fig. 77), VI, or abdu- 

 centes arise from the posterior margin of the pons Varolii, 

 and each is distributed to one muscle of the eyeball. 



The seventh pair (facial nerves), VII, appear also at the 

 posterior margin of the pons. They are distributed to most 

 of the muscles of the face and scalp. 



The eighth pair (auditory nerves) arise close to the facial. 

 They are the nerves of hearing and are distributed entirely 

 to the internal ear. 



The ninth pair (glossopharyngeals), IX, arising close to 

 the auditories, are distributed to the mucous membrane of 

 the pharynx, the posterior part of the tongue, and the middle 

 ear. 



The tenth pair (pneumo gastric nerves or vagi), X, arise 

 from the sides of the medulla oblongata. Each gives branches 

 to the pharynx, gullet and stomach, the larynx, windpipe 

 and lungs, and to the heart. The vagus runs farther through 

 the body than any other cranial nerve. 



The eleventh pair (spinal accessory nerves), XI, do not 

 arise mainly from the brain but by a number of roots attached 

 to the lateral columns of the cervical portion of the spinal 



