. The anatomy of the domestic animals . Veterinary anatomy. THE SPHENOID BONE 53 noidalis), which overhes the entrance to the optic foramina. The median ridge is termed the ethmoidal spine, since it fits into a notch of the cribriform plate of the ethmoid bone and joins the crista galli. (2) Just behind this and at a lower level is a smooth transverse depression, the optic groove (Sulcus chiasmatis), on which the optic chiasma rests. (3) From each end of this groove the optic foramen (Foramen opticum) passes forward and outward to terminate in the posterior part of the orbital fossa.^ (4) Near
. The anatomy of the domestic animals . Veterinary anatomy. THE SPHENOID BONE 53 noidalis), which overhes the entrance to the optic foramina. The median ridge is termed the ethmoidal spine, since it fits into a notch of the cribriform plate of the ethmoid bone and joins the crista galli. (2) Just behind this and at a lower level is a smooth transverse depression, the optic groove (Sulcus chiasmatis), on which the optic chiasma rests. (3) From each end of this groove the optic foramen (Foramen opticum) passes forward and outward to terminate in the posterior part of the orbital fossa.^ (4) Near the posterior end is a central depression, the hypo- physeal or pituitary fossa (Fossa hypophyseos), which lodges the hypophysis cerebri or pituitary body. On each side of this is a shallow groove for the internal carotid arterj' and the cavernous sinus. The anterior end is expanded, and joins the eth- moid and palatine bones; it is excavated to form the sphenoidal sinuses. These cavities extend back as far as the optic groove, and are usually continuous in front with the cavities in the vertical parts of the palate bones;- they are separated by a com- plete septum which is not always median. The posterior end is flat and is joined to the basilar part of the occipital; at the line of junction there is dorsally a slight trans- verse elevation, the spheno-occipital crest (Crista spheno-occipitalis). The orbital wings (Alse orbitales) curve dorso-laterally from of the body of the presphenoid. Their cerebral surface is concave, and is marked by digital impres- sions (Impressiones digitatse) for the gyri of the cerebrum. The lateral surface is con- vex and is largely concealed by the overlap- ping temporal wing and the squamous tem- poral and frontal bones; a narrow part of it (Facies orbitalis) is uncovered on the medial wall of the orbital cavity at the sphenoidal notch of the frontal bone. The dorsal bor- der unites with the frontal bone at the spheno-frontal suture. T
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