974 THE NERVOUS SYSTEM 



palatine nerve gives off the posterior inferior nasal nerves. These nerves pass 

 through small openings in the perpendicular plate of the palate bone to supply the 

 mucous membrane covering the posterior part of the inferior nasal concha (tur- 

 binated bone) and the adjacent portions of the middle and inferior meatuses of the 

 nose. 



The posterior or small palatine nerve passes downwards through a lesser pala- 

 tine foramen (accessory palatine canal) , and enters the soft palate , distribut i ng branches 

 to that organ, to the uvula, and to the tonsil. It was formerly believed to convey 

 motor fibres from the facial nerve to the levator palati and azygos uvula3, but it is 

 now believed that these muscles are supplied by the spinal accessory nerve through 

 the pharyngeal plexus (fig. 699). 



The middle (external) palatine nerve, the smallest of the three, traverses a 

 lesser palatine foramen and supplies twigs to the tonsil and to the adjacent part of the 

 soft palate (fig. 699). 



Posterior branch. The pharyngeal branch, which is of small size, passec, 

 backwards and somewhat inwards through the pharyngeal (pterygo-palatine) canal 

 accompanied bya branch df the spheric-palatine artery. It is distributed to the mucous 

 membrane of the uppermost part of the pharynx, to the upper part of the posterior 

 nares, to the opening of the Eustachian tube, and to the lining of the sphenoidal sinus. 



THE OTIC GANGLION 



The otic or Arnold's ganglion is a small reddish-grey body which is associated 

 with the mandibular nerve. It lies deeply in the zygomatic fossa, immediately 

 below the foramen ovale, on the inner side of the trunk of the mandibular nerve. 

 It is in relation internally with the tensor palati, which separates it from the Eusta- 

 chian tube. In front of it is the posterior border of the pterygoideus internus, 

 and behind it lie the middle and small meningeal arteries. It is compressed 

 laterally, and its greatest diameter, which lies antero-posteriorly, is about three 

 millimetres. 



Roots. The ganglion is closely connected with the nerve to the pterygoideus 

 internus, through which it may receive a motor root from the mandibular nerve. 

 Through the small superficial petrosal nerve, which joins the upper and back part 

 of the ganglion, it receives a motor root from the seventh nerve and a sensory root 

 from the ninth nerve. It receives also some root fibres frcm the Vidian nerve. The 

 sympathetic root is derived from the sympathetic plexus on the middle meningeal 

 artery. 



Branches. The communicating branches which pass from the ganglion are: 

 (1) The filaments to the chorda tympani; (2) filaments to the auriculo-temporal 

 nerve; (3) filaments to the spinous nerve (the recurrent branch of the mandibular 

 nerve). The branches of distribution are muscular branches to the tensor tympani, 

 and tensor veli palatini. 



THE SUBMAXILLARY GANGLION 



The submaxillary ganglion is suspended from the lingual division of the mandi- 

 bular nerve by anterior and posterior branches. It is a small reddish body, of tri- 

 angular or fusiform shape, which lies between the mylo-hyoideus and hyo-glossus 

 and above the duct of the submaxillary gland. 



Roots. The motor and sensory roots are received from the lingual nerve. The 

 motor fibres come from the chorda tympani after it has joined the lingual, and the 

 sensory fibres come directly from the lingual nerve. The sympathetic root is formed 

 by filaments from the sympathetic plexus on the facial artery. 



Branches. (a) Five or six glandular branches are given to the submaxillary 

 gland and to Wharton's duct. 



(6) Branches to the lingual nerve and the sublingual gland. 



(c) To the mucous membrane of the floor of the mouth. 



THE SIXTH NERVE THE ABDUCENS 



The abducens on each side arises from the cells of a nucleus which lies in the grey 

 substance of the floor of the fourth ventricle in the region of the inferior part of the 

 pons. The nucleus is situated close to the middle line, ventral to the striffi acustics and 



