220 THE ANATOMY OF THE HORSE. 



3. The Staphyline Nerve passes by the groove of the same name to the 

 soft palate. 



4. The Spheno-palatine Nerve enters the foramen of the same name, 

 and is distributed to the nasal mucous membrane. 



The Spheno-palatine (Meckel's) Ganglion. This is a small, greyish, 

 elongated and fusiform enlargement, generally adherent to the spheno- 

 palatine nerve. Slender branches radiate from it, and are divided into 

 afferent and efferent filaments. 



Afferent Filaments. — 1. The Vidian Nerve, which enters its posterior 

 extremity. This is a composite nerve formed by the union of the large 

 superficial petrosal branch of the 7th with a sympathetic filament. 

 Traced upwards, it enters a minute foramen — the lower orifice of the 

 vidian canal. At the upper orifice of the canal it enters the sub- 

 sphenoidal confluent, and passes into the cavernous sinus by the 

 foramen lacerum basis cranii. There it separates into its petrosal 

 and sympathetic branches. The former enters a small foramen to 

 the inner side of the Eustachian orifice of the petrous temporal bone, 

 penetrates to the aqueduct of Fallopius, and joins the geniculate 

 ganglion of the 7th nerve. The sympathetic branch of the vidian 

 nerve joins the cavernous plexus. 



2. Short branches passing from the spheno-palatine nerve to the 

 posterior part of the ganglion. 



The vidian nerve is supposed to combine the motor and sympathetic 

 roots of the ganglion ; the spheno-palatine branches represent its 

 sensory root. 



Efferent Branches. — Some of these pass to the ocular sheath, to the 

 ophthalmic vessels, and to the muscles and other accessory parts of the 

 eye. Others join the spheno-palatine, palatine, superior dental, and 

 staphyline nerves. The latter it is believed derives from this source 

 the motor filaments which it conveys to the levator palati muscle. 



the occipito-atlantal articulation. 



This joint possesses two synovial sacs and an enveloping capsule, 

 with accessory fasciculi above and at each side which are sometimes 

 described as distinct ligaments — the cruciform and styloid. 



The Occipito-Atlantal Ligament is membranous, and closes the 

 interval between the occiput and atlas. It is attached to the occiput 

 at the upper and lower edges of the foramen magnum, and to the outer 

 side of the condyles. Its posterior edge is fixed to the anterior border 

 of the atlas. The most superior fibres pass obliquely, the right and left 

 fibres intercrossing. This is the so-called cruciform ligament. On each 

 side a thickened cord-like portion passes to be inserted into the styloid 

 process of the occipital bone, and these constitute the styloid ligaments. 



