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THE NERVOUS SYSTEM. 



The Spheno-palatine Ganglion (Fig. 396). 



The spheno-palatine ganglion (Meckel's), the largest of the cranial ganglia, is 

 deeply placed in the spheno-maxillary fossa, close to the spheno-palatine foramen. 

 It is triangular or heart-shaped, of a reddish-gray color, and is situated just below 

 the superior maxillary nerve as it crosses the fossa. 



Its Branches of Communication. Like the other ganglia of the fifth nerve, it 

 possesses a motor, a sensory, and a sympathetic root. Its sensory root is derived 

 from the superior maxillary nerve through its two spheno-palatine branches. These 

 branches of the nerve, given off in the spheno-maxillary fossa, descend to the 

 ganglion. Their fibres, for the most part, pass in front of the ganglion, as they 

 proceed to their destination, in the palate and nasal fossa, and are not incorporated 

 in the ganglionic mass ; some few of the fibres, however, enter the ganglion, 

 constituting its sensory root. Its motor root is derived from the facial nerve 

 through the large superficial petrosal nerve, and its sympathetic root from the 

 carotid plexus, through the large deep petrosal nerve. These two nerves join together 

 to form a single nerve, the Vidian, before their entrance into the ganglion. 



FIG. 396. The spheno-palatine ganglion and its branches. 



The large superficial petrosal branch (nervus petrosus superjicialis major) is 

 given off from the geniculate ganglion of the facial nerve in the aqueductus Fal- 

 lopii ; it passes through the hiatus Fallopii ; enters the cranial cavity, and runs 

 forward contained in a groove on the anterior surface of the petrous portion of the 

 temporal bone, lying beneath the dura mater. It then enters the cartilaginous 

 substance which fills in the foramen lacerum medium basis cranii, and, joining 

 with the large deep petrosal branch, forms the Vidian nerve. 



The large deep petrosal branch (nervus petrosus profundus) is given off from 

 the carotid plexus, and runs through the carotid canal on the outer side of the 

 internal carotid artery. It then enters the cartilaginous substance which fills in 

 the foramen lacerum medium, and joins with the large superficial petrosal nerve to 

 form the Vidian. 



The Vidian nerve, formed in the cartilaginous substance which fills in the 

 middle lacerated foramen by the junction of the two preceding nerves, passes 



