SPHENO- PALATINE GANGLION 319 



of the nasal cavity, and one in the pharyngeal canal (O.T. 

 pterygo-palatine or pharyngeal nerve). They are distributed 

 to the muco-periosteum of the posterior part of the roof of 

 the nasal cavity, to the adjacent parts of the wall of the 

 pharynx, to the sphenoidal air sinus, and to the pharyngeal 

 part of the auditory tube. 



The descending branches are the palatine nerves, and with 

 them are incorporated the posterior inferior nasal nerves. 

 The palatine nerves are three in number, anterior (O.T. great 

 or posterior palatine), middle, ?.nd posterior. As a rule the 

 three spring, by a common trunk, from the lower aspect of 

 the ganglion. The trunk descends in the pterygo-palatine 

 canal, which has been opened up already, but to expose the 

 nerves a dense fibrous investment must also be removed. 

 The nerve-trunk will then be seen breaking up into its con- 

 stituent parts. 



Dissection. Trace, in the first instance, the two smaller 

 nerves viz., the middle and posterior palatine branches. They 

 leave the main canal and enter the lesser palatine canals, which 

 conduct them through the pyramidal process of the palate bone. 

 It is well to secure the nerves as they emerge from the lower 

 openings of the canals, before opening the canals. The dissector 

 can readily find them by dissecting posterior to the hamulus of 

 the medial pterygoid lamina and gently separating the soft parts 

 from the under aspect of the pyramid of the palate bone. As 

 the dissection is being made from the medial side, the middle 

 palatine nerve will be first encountered, and it will be seen to 

 pass backwards into the soft palate, under cover of the tendinous 

 expansion of the tensor veli palatini. 1 The tensor must be 

 divided, in order that the nerve may be followed to its distribu- 

 tion. The posterior palatine nerve will be found issuing from 

 its canal a short distance to the lateral side of the preceding 

 nerve. It is distributed to the soft palate in the neighbourhood 

 of the palatine tonsil. It is smaller than the middle palatine 

 nerve, and is sometimes absent. The large anterior palatine 

 nerve should now be followed onwards to the hard palate. To 

 do that, open up the lower part of the pterygo-palatine canal by 

 removing a small portion of the posterior and lateral part of the 

 horizontal plate of the palate bone. 



The anterior palatine nerve is the largest branch of the 

 spheno-palatine ganglion. It descends through the pterygo- 

 palatine canal, accompanied by the great palatine branch of 

 the internal maxillary artery ; it enters the palate through the 

 greater palatine foramen and runs forwards, in a groove on the 



1 The present is a good opportunity to observe the corrugated or wrinkled 

 appearance of the tendon of the tensor, as it passes under the hamulus. 



