I 6 EQUINE ANATOMY. 



SPHENOID. 



The sphenoid (a wedge) serves to connect the bones of the 

 head and face, being wedged in between the occipital behind, the 

 ethmoid and frontal in front, the parietals and temporals laterally. 

 It is divided into a body and two wings. 



The body shows on its internal surface — 



The optic fossa, a transverse depression for the optic nerves, 

 ending in the optic foramina, which open into the orbit. 



The seita turcica or pituitary fossa, behind this, receiving the 

 pituitary body. 



The wings projecting from the body and articulating with the 

 frontal. 



Two fissures outside the sella tui'cica, the inner one lodging the 

 cavernous sinus. 



The supra-sphenoidal canals, the upper one called the great 

 sphenoidal fissure, the lower the foramen I'otundum, the middle 

 opening near the optic. 



The External or Inferior Surface shows — 



Outside, the vidian canal opening into the orbit. 



The internal pterygoid plate (pterygoid bone) outside the 

 vomer, flattened laterally. 



Its internal face forms part of the pharyngeal walls. 



At its base is found the vidian canal (see above). 



Its apex forms the hamular (hooked) process, passing backward 

 and serving for the passage of the tendon of the tensor palati. 



The extej-nal pterygoid or sub-sphenoidal process lying outside 

 the preceding. 



Above this the oi^^mngoi \h^ sub-sphenoidal canal yN\\\Q\\ opens 

 into the orbit. 



Below two fissures for articulation with the vomer. 



The superior ox poste?'ior hoxAtr is continuous with the basilar 

 process of the occipital, and on each side forms the inner bound- 

 aries of the lacerated foramen. Three notches are also seen, for 

 the passage of the carotid a7'tery, \\\t foratnen ovale for the infer- 

 ior maxillary nerve, and one for the middle 7neningeal artery, the 

 foramen spinosujn. 



The anterior or infe?'ior border shows — 



The sphenoidal sinuses, excavations continuous with the eth- 

 moidal plate. 



The lateral borders show — 



