THE SPHENO-PALATINE GANGLION. 243 



the mucous membrane behind the incisor teeth, and communicate with the great 

 palatine nerve. In its course along the septum, small filaments are furnished from 

 the naso-palatine nerve to the pituitary membrane. 



POSTERIOR BRANCHES. The branches directed backwards from the spheno- 

 palatine ganglion are the Vidian and pharyngeal nerves. 



The Vidian nerve, arising from the back part of the ganglion, which seems to be 

 prolonged into it, passes backwards through the Vidian canal to the foramen lacerum, 

 where it divides into thQ great superficial and the great deep petrosal nerves. While 

 in its canal, the Vidian nerve gives some small nasal branches, which supply the 

 membrane of the back part of the roof of the nose and septum, as well as the mem- 

 brane covering the end of the Eusbachian tube ; and it is joined by the sphenoidal 

 filament from the otic ganglion (p. 249). 



The large superficial petrosal nerve (fig. 159,8), entering the cranium on the 

 outer side of the carotid artery and beneath the Gasserian ganglion, is directed 

 backwards in a groove on the petrous portion of the temporal bone to the hiatus 

 Fallopii, and is thus conducted to the aqueductus Fallopii, where it joins the 

 geniculate ganglion of the facial nerve. 



The large deep petrdsal nerve (fig. 159, 9), shorter than the other, is of a reddish 

 colour and softer texture : it is directed backwards, and on the outer side of the 

 carotid artery ends in the filaments of the sympathetic surrounding that vessel. 



In accordance with the view taken of the ganglia connected with the fifth nerve 

 (p. 237), the superficial and deep petrosal parts of the Vidian nerve may be regarded 

 as the motor and sympathetic roots respectively of the spheno-palatine ganglion, the 

 spheno-palatine nerves constituting its sensory root. The ganglion may also receive 

 fibres from the glosso-pharyngeal uerve, conveyed to it through the small and large 

 deep petrosal nerves (p. 260, and fig. 170) : this connection is sometimes described 

 as a second sensory root. 



The pharyngeal nerve is small, and springs from the back of the ganglion, often 

 in common with the Vidian nerve. It enters the pterygo-palatine canal with an 

 artery, and is lost in the lining membrane of the pharynx behind the Eustachian 

 tube. 



SUMMARY. The superior maxillary nerve, with Meckel's ganglion, supplies the 

 integument of the cheek and the fore part of the temple, the lower eyelid, the side 

 of the nose, and the upper lip ; the upper teeth ; the lining membrane of the nose ; 

 the mucous membrane of the upper part of the pharynx, of the antrum of Highmore, 

 and of the posterior ethmoidal cells ; the soft palate, tonsil, and uvula, and the 

 glandular and mucous structures of the roof of the mouth. 



III. INFERIOR MAXILLARY NERVE. 



The lower maxillary nerve (n. mandibularis), the third and largest division of the 

 fifth, is made up of two portions of unequal size, the larger being derived from the 

 Gasserian ganglion, and the smaller being the slender motor root of the fifth nerve. 

 These two parts leave the skull by the foramen ovale in the sphenoid bone, and 

 unite immediately after their exit. Three or four mm. below the base of the skull, 

 and under cover of w the external pterygoid muscle, the nerve separates into two 

 primary divisions, one of which is higher in position and smaller than the other. 



The small, anterior, or upper portion (n. masticatorius) receives the greater part 

 of the fibres of the motor root, and breaks up into temporal, masseteric, external 

 pterygoid, and buccal branches, of which the last alone is a sensory nerve. The 

 large, posterior, or lower portion is chiefly sensory, and divides into auriculo- 

 temporal, lingual, and inferior dental nerves ; it likewise supplies through the last- 



