756 THE SERVO US SYSTEM 



passing through the anterior of the two foramina. In the lower })art of the anterior 

 I)alatine canal the two nerves form a plexiform conmiunieation ( formerly descrihed 

 as Chxiuet's ganglion) and furnish twigs to the anterior ])art of the hard palate. 

 In this situiition they coiiiniunieate with the anterior palatine nerves. 



(8) Descending branches. — The descending l)ranches are the great or anterior, 

 the posterior, and the external palatine nerves. Like the internal set of hranches, 

 tliey are in part derived from the ganglion and in part directly continuous with 

 tlie spheno-palatine nerves. 



The great or anterior palatine nerve arises from the inferior angle of Meckel's 

 ganglion, and passes downwards tlirough the posterior palatine canal, accompanied 

 hy the descending palatine artery. Emerging from the canal, it divides into two 

 or three branches, which pass forwards in grooves in the hard palate and su])ply 

 the glands and mucous membrane of the hard palate and the gums on the inner 

 ;ispect of the alveolar border of the upper jaw. During its course through the 

 posterior })a]atine canal, the anterior palatine nerve gives off, usually two, inferior 

 nasal nerves. These ner\^es pass through small openings in the perpendicular 

 plate of the palate bone to supply the mucous membrane covering the back parts of 

 the inferior turVjinated bone and lining the middle and inferior meatuses of the nose. 



The posterior or small palatine nerve passes downwards through the acces- 

 sory i)alatine canal, and enters the soft palate, distril^uting 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 uvuhe muscles, but these muscles 

 are now known to be supplied l)y the spinal accessory nerve, through the pharyn- 

 geal plexus. 



The external palatine nerve, the smallest of the three, traverses the external 

 ])alatine canal, and supplies twigs to the tonsil and to the adjacent part of the soft 

 palate. 



(4) Posterior branch. — The \'idian is considered by some anatomists to be a 

 branch, in which case it w'ould be classed here. We have, however, regarded it 

 as the united motor and sympathetic root of the ganglion; therefore, the pharyn- 

 geal branch only remains to l)e described. 



The pharyngeal branch is of small size, and passes backwards and somewhat 

 inwards through the ])tery go-palatine canal, accompanied by the pterygo-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. 



Third or Mandibular Division of the Fifth Nerve 



The mandibular ( inferior maxillary ) division is the largest of the three 

 divisions of tlie fifth nerve, and is formed, as Ix-fore stated, by the union of two 

 distinct parts, namely, the entire motor root of the fifth nerve and a large bundle of 

 fibres derived from the sensory root and traversing the Gasserian ganglion. These 

 two parts pass through the foramen ovale and unite immediately outside the skull 

 to form a large trunk which terminates almost directly after its formation by 

 dividing into a smaller anterior and a larger posterior portion. The anterior portion 

 is chiefly motor, and the posterior division mainly sensory in function. Previous 

 to its division, two branches arise from the trunk of the nerve, namely, the recur- 

 rent nerve and tin- nerve to the internal pterygoid. 



(1) The recurrent nerve enters the cranium through the foramen s])inosimi, 

 ac(;ompanying the middle meningeal artery, and divides into an anterior and a 

 })osterior l)ranch. The anterior branch conmmnicates with the meningeal l)ranch 

 of the maxillary division of the fifth nerve, furnishes filaments to the dura mater, 

 and ends in the osseous substance of the great wing of the sphenoid. The posterior 

 branch traverses the petro-squamous suture and ends in the lining membrane of 

 the mastoid cells. 



(2) The nerve to the internal pterygoid passes under cover of a dense layer 

 of fascia deprived from an expansion of the ligamentum ])teryg(»-s])in()sum, and 

 enters the deej) surface of the muscle. Near its connnencement this nerve furnishes 

 a motor root to the otic ganglion. 



