THE SPHENOID BONE 53 
noidalis), which overlies 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 
artery 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 (Ale orbitales) curve 
dorso-laterally from the sides of the body of 
the presphenoid. Their cerebral surface is 
concave, and is marked by digital impres- 
sions (Impressiones digitate) 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- 
Fic. 31—Spxenorm Bone snp Basitak Part OF 
OcctriraL BoNE oF NEW-BORN Fost; Dorsat 
VIEW. 
der unites with the frontal bone at the 
spheno-frontal suture. The anterior border 
joins the ethmoid at the spheno-ethmoidal 
suture; at its lower part it concurs with the 
ethmoid and frontal in the formation of the 
ethmoidal foramen (Foramen ethmoidale).* 
The posterior border is overlapped by the 
temporal wing and the squamous temporal. 
C, Body of presphenoid; C’, body of postsphe- 
noid; B.o., basilar part of occipital bone; A.o., orbital 
wing of sphenoid bone; A.t., temporal wing of sphe- 
noid bone; 1, 1, optic foramina; 2, optic groove; 3, 
hypophyseal fossa; 4, 5, grooves; 6, ethmoidal 
notch; 7, ethmoidal spine; 8, junction with crib- 
riform plate’ of ethmoid bone; 9, junction with 
frontal bone; 10, junction with squamous temporal 
bone; 11, margin of foramen lacerum anterius; 12, 
spheno-occipital crest; 13, junction of basilar part 
of occipital bone with lateral part. 
The root of the wing is perforated by the 
optic foramen (Foramen opticum). Immedi- 
ately below and behind the latter (7. e., beneath the root) is the foramen orbitale. 
Below this, and separated from it usually by a thin and often incomplete plate, is a 
larger opening, the foramen rotundum, which is bounded externally by the root of 
the pterygoid process. 
The temporal wings (Alz temporales) extend outward and somewhat upward 
from the body of the postsphenoid; they are smaller than the orbital wings and 
1 This foramen might well be called a canal, since it is an inch or more in length. 
2 The cavity so formed may be termed the sphenopalatine sinus. The sphenoidal sinus may 
be a separate cavity which communicates only with the ventral ethmoidal meatuses; this arrange- 
Ment exists in about a third of the cases according to Paulli. 
8 Also called the internal orbital foramen. 
