402 HEAD AND NECK 



of the palate bone, at a point between the posterior extremities 

 of the middle and inferior conchse. It divides into an ascend- 

 ing and descending branch. Both run anteriorly the former on 

 the middle concha, the latter on the inferior concha. The lower 

 of the two inferior nasal nerves appears through a foramen 

 in the perpendicular part of the palate bone, immediately 

 posterior to the inferior concha, upon which it is distributed. 



The anterior ethmoidal nerve (O.T. nasal) should be ex- 

 posed as it descends in the groove upon the deep surface of 

 the nasal bone (p. 393). It gives medial branches to the 

 septum, and lateral branches to the muco-periosteum over the 

 anterior part of the lateral wall, and to the anterior parts of 

 the middle and inferior conchae. 



The main artery of supply to the nasal muco-periosteum 

 is the spheno-palatine, a branch of the internal maxillary. It 

 gains entrance to the nasal cavity through the spheno-palatine 

 foramen, in company with the posterior superior nasal nerves. 

 The septal branch of this vessel accompanies the naso-palatine 

 nerve, whilst others are distributed upon the lateral wall of the 

 cavity. Several twigs are given also by the descending palatine 

 branch of the internal maxillary and the two ethmoidal arteries^ 

 but these are small and will be seen only in cases where the 

 injection of the subject has been unusually successful. 



SPHENO-PALATINE GANGLION AND INTERNAL 

 MAXILLARY ARTERY. 



The spheno-palatine ganglion is situated in the pterygo- 

 palatine fossa on the lateral side of the spheno-palatine fora- 

 men ; and at this stage it can be exposed best by dissecting 

 from the medial or nasal side. 



Dissection, The muco-periosteum has already been removed from 

 the posterior part of the lateral wall of the nasal cavity, and the inferior 

 nasal branches of the anterior palatine nerve have been found piercing the 

 perpendicular part of the palate bone. The dissector cannot fail to notice 

 the course taken by the trunk from which these filaments arise. The lamina 

 of bone which forms the medial wall of the pterygo-palatine canal is so 

 thin that the nerve can be distinctly seen through it. By carefully opening 

 up this canal with a chisel, and following the anterior palatine nerve upwards, 

 the dissector will be led to the ganglion in the pterygo-palatine fossa. 

 The naso-palatine nerve should at the same time be traced to its origin. 

 The ganglion is so hemmed in by the bony walls of the fossa that it is very 

 difficult to display it thoroughly ; but by removing the orbital process of the 



