154 OSTEOLOGY. 
The following foramina open into the zygomatic fossa—the foramen ovale, 
foramen spinosum, posterior dental foramina, inferior dental foramen, minute 
foramina for the transmission of emissary veins; of these one of large size is 
occasionally present, the foramen of Vesalius. 
Spheno-Maxillary Fossa.—This space, which corresponds to the angular interval 
between the pterygo-maxillary and spheno-maxillary fissures, and which lies 
between the maxilla in front and the root of the pterygoid process behind, 
bounded internally by the vertical plate of the palate bone, which separates it 
from the nasal cavity, with which, however, it communicates by means of the 
spheno-palatine foramen, which lies between the orbital and sphenoidal processes of 
the palate bone and the under surface of the body of the sphenoid. Opening 
into this fossa, above and behind, are the foramen rotundum, the Vidian canal and 
the pterygo-palatine canal from without inwards, whilst below is the superior 
orifice of the posterior palatine canal, together with openings of the accessory 
posterior palatine canals. Its roof is formed by the under surface of the body of 
the sphenoid and the orbital plate of the palate bone. Anteriorly it lies in relation 
to the apex of the orbit, with which if communicates by means of the spheno- 
maxillary fissure; whilst externally, as already stated, it communicates with the 
zygomatic fossa through the pterygo-maxillary fissure. 
NORMA OCCIPITALIS. 
This view of the cranium includes the posterior halves of the two parietal 
bones above, the tabular part of the occipital bone below, and the mastoid portions 
of the temporal bones on either side inferiorly. The shape of this aspect of the 
skull varies much, but ordinarily the greatest width corresponds to the level of the 
parietal eminences. The sutures on this view of the calvaria display a tri-radiate 
arrangement, one limb of which is vertical, and corresponds to the posterior part of 
the interparietal or sagittal suture (sutura sagittalis). The other two limbs pass 
outwards and downwards in the direction of the mastoid processes, uniting the two 
parietal bones in front with the occipital bone behind ; these constitute the ‘- shaped 
lambdoid suture (sutura lambdoidea). The point of confluence of the sagittal and 
lambdoid sutures is called the lambda. This can generally be felt in the living, 
owing to the tendency of the tabular part of the occipital to project slightly 
immediately below this spot. About one inch and a quarter above the lambda the 
two small parietal foramina (foramina parietalia) are seen, through which pass the 
small emissary veins of Santorini, which connect the intracranial venous system 
with the superficial veins of scalp. These small holes lie about 55, of an inch apart 
on either side of the sagittal suture, which here, for the space of about an inch, 
displays a simplicity of outline in striking contrast with its serrated arrangement 
elsewhere. The term obelion is applied to a point on the sagittal suture in line 
with the two parietal foramina. The lambdoid suture is characterised by great 
irregularity of outline, and not unfrequently chains of separated ossicles are met 
with in it, the so-called Wormian bones. The tabular part of the occipital bone is 
divided into two parts by the superior curved line (linea nuch superior), the 
central part of which forms the external occipital protuberance (protuberantia 
occipitalis exterior). The part above, called the occipital surface (planum occipitale), 
comes within our present consideration ; the part below, the nuchal surface (planum 
nuchale), though seen in perspective, had best be considered when the base is 
examined. A little above the level of the superior curved line the occipital surface 
is crossed on either side by a faint lunated line, the highest curved line (linea 
nuch suprema) to which are attached the occipitales muscles and the epicranial 
aponeurosis. The projection of the occipital surface varies much in individual 
skulls; most frequently it overhangs the external occipital protuberance, forming a 
distinct boss; exceptionally, however, the latter may be the most projecting part of 
the bone. The extremity of the superior curved line on either side corresponds to 
the position of the asterion (p. 149). External to these points the outline of the 
skull is determined by the downward projection of the mastoid processes, the inner 
surfaces of which are deeply grooved for the attachment of the posterior bellies of 
