962 THE NERVOUS SYSTEM 



The Spheno-palatine or Meckel's Ganglion 



This ganglion is associated with the maxillary nerve (fig. 743) . It is a small 

 reddish-gre}' body of triangular form, which is flattened at the sides, and measures 

 about five millimetres from before backward. It lies deeply in the pterygo- 

 palatine (spheno-maxillary) fossa at the lateral side of the spheno-palatine fora- 

 men and in front of the anterior end of the pterygoid (Vidian) canal. It is 

 attached to the maxillary nerve, from which it receives its sensory root, and it is 

 connected with the Vidian nerve, which furnishes it with motor and sympathetic 

 filaments (fig. 739). 



The exact position of the ganghon depends upon the size and shape of the sphenoidal air 

 cells. When these are small, or high and narrow, the ganghon lies lateral to them; when they 

 are large, or broad and flat, the ganglion lies inferior to them. Sometimes it may lie anterior 

 to them if the cells are short from in front backward. The ganglion may be reached with ease 

 by chipping away the bone around the sphenoidal air cells after the skuU is divided sagitally. 



Roots.- — (a) Its motor root, consisting of visceral motor fibres of the glosso-palatine nerve, 

 is contained in the great superficial petrosal nerve which is incorporated in the Vidian nerve. 

 It springs from the anterior angle of the geniculate ganglion and passes through the hiatus 

 of the facial canal (hiatus Fallopii) into the middle fossa of the cranium, where it runs forward 

 and medialward, in a groove on the upper surface of the petrous part of the temporal bone, to 

 the foramen lacerum, and in this part of its course it passes beneath the semilunar (Gasserian) 

 ganglion and the masticator nerve. In the foramen lacerum it joins with the great deep petrosal 

 nerve to form the Vidian nerve (nerve of the pterygoid canal), which passes forward through the 

 pterygoid (Vidian) canal and its motor and sympathetic fibres terminate in the spheno-palatine 

 ganghon in the pterygo-palatine (spheno-maxillary) fossa. The great superficial petrosal nerve 

 contains sensory as well as sympathetic and motor fibres. The sensory fibres pass through the 

 ganglion and, in the small palatine nerve, descend to the soft palate, where they terminate in 

 the epithelium covering it and some are probably concerned with peripheral taste organs 

 found there. They arise from the cells of the geniculate ganglion and therefore belong to the 

 glosso-palatine nerve. 



(6) The sympathetic root is the great deep petrosal portion of the Vidian nerve. This 

 root, which is of reddish colour and of soft texture, springs from the carotid plexus which lies 

 on the outer side of the internal carotid artery in the carotid canal. It enters the foramen 

 lacerum through the apex of the petrous portion of the temporal bone, and unites with the great 

 superficial petrosal branch of the facial nerve to form the Vidian nerve. The great superficial 

 petrosal nerve also carries sympathetic fibres to the spheno-palatine ganglion, derived from the 

 geniculate ganglion and from the tympanic plexus. 



The Vidian nerve [n. canalis pterygoidei] commences by the union of the great superficial 

 and deep petrosal nerves in the foramen lacerum, and runs forward through the pterygoid 

 (Vidian) canal to the pterygo-palatine (spheno-maxillary) fossa to the spheno-palatine ganglion. 

 The Vidian nerve often may be seen in a ridge of bone along the fioor of the sphenoidal cells 

 and its direction there depends upon the position of the spheno-palatine ganglion. While it is 

 in the pterygoid canal the Vidian nerve is joined by a sphenoidal filament from the otic ganglion, 

 and it gives branches to the upper and back part of the roof and septum of the nose, and to the 

 lower end of the Eustachian tube. 



(c) The sensory roots consist of the sensory fibres mentioned above in the great superficial 

 petrosal nerve and of usually two spheno-palatine branches from the maxillary nerve. The 

 majority of the fibres of these roots do not join the ganglion, but pass by its medial side and 

 enter the palatine branches. 



Branches. — The branches of the ganglion, containing sensory, vaso-motor and secretory 

 fibres, are orbital or ascending, internal or nasal, descending or palatine, and posterior or pharyn- 

 geal. 



Ascending branches. — The orbital or ascending branches are two or three small twigs 

 which enter the orbit through the inferior orbital (spheno-maxillary) fissure and proceed, within 

 the periosteum, to the inner wall of the orbit, where they pass through the posterior ethmoidal 

 foramen and through the foramina in the suture behind that foramen to be distributed to the 

 mucous membrane which lines the posterior ethmoidal cells and the sphenoidal sinus. 



Internal branches. — The internal or nasal branches are derived in part from the medial 

 side of tlio ganglion, l>ut are also largely made up of fibres which pass from the spheno-palatine 

 branches of the niaxillary nerve without traversing the ganglionic substance. They are dis- 

 posed in two .sets, the lateral and the medial (septal) posterior superior nasal branches. 



The lateral posterior superior nasal branches are six or seven small twigs which pass through 

 the spheno-palatine foriunen, and are distributed to the mucous membrane covering the poster- 

 ior parts of the superior and middle nasal concha; (turbinated bones) (fig. 732). They also 

 furnish twigs to tlie lining mcnil>iane of the posterior etlimoidal cells. 



Tlie medial posterior superior nasal (septal) branches, two or three in number, pass medial- 

 ward through the spheno-i)alatine foramen. They cross the roof of the nasal fo.ssa to reach the 

 back i)art of t he nasal sej)tuni, where the smaller twigs terminate. The largest nerve of the set, 

 the naso-palatine nerve, or nerve of Cotunnius, runs downward and forward in a groove in the 

 vomer betw(M'n th(' periostcuin and the iniKHtus nicnibrane to the incisive (anterior [)alatine) 

 canal, where it (■(>innumicat(!s with the na.sal branch of the anterior superior alveolar nerve. 

 The two naso-palatine nerves then j)ass through the foramina of Scarpa in the intermaxillary 

 suture, the left nerve pa.ssing through the anterior of the two foramina. In the lower part 

 of the incisive (anterior i)alatine) canal the two nerves form a i)loxiform communication (for- 



