NORMA LATERALIS OF THE SKULL. 153 
the small meningeal artery through the foramen ovale, and the middle meningeal 
artery and its companion veins through the foramen spinosum. <A part of the 
squamous temporal also forms a small portion of the roof of this fossa; it consists 
of a triangular area immediately in front of the eminentia articularis, and between 
it and the anterior root of the zygomatic process of the temporal, which is here 
curving inwards and forwards, to become continuous with the infratemporal crest. 
Internally this surface is continuous with the zygomatic surface of the great wing 
of the sphenoid, separated from it, however, by the hinder part of the spheno- 
squamosal suture. 
When the lower jaw is in position, the zygomatic fossa is concealed by the 
ramus of the mandible, the inner surface of which, in its upper half, forms the outer 
wall of that space. Viewed from the outer side, the ramus of the inferior maxilla 
displays considerable differences in different skulls. These are mainly due to varia- 
tions in its width and in the nature of the angle which it forms at its fusion with 
the body of the bone. A considerable interval separates the posterior border of the 
ramus from the front of the mastoid process. Within this space may be seen the 
free inferior edge of the tympanic plate (vaginal process), from which, just below 
the external auditory meatus, the styloid process of the temporal bone is observed 
passing downwards and slightly forwards. The width and height of the coronoid 
process vary much, oftentimes reaching the level of the top of the condyle. Its 
extremity, when the lower jaw is closed, les just within the fore part of the zygo- 
matic arch, at other times rising to a much higher level so that its point may be 
seen above the level of the upper border of the zygomatic arch. The posterior 
edge of the coronoid process forms the anterior border of the sigmoid notch, and 
limits in front the interval left between the lower border of the posterior half of 
the zygomatic arch and the upper hollowed edge of the ramus. On looking into 
this interval, the floor of the zygomatic fossa may be seen, formed anteriorly by the 
external pterygoid plate; whilst posteriorly it is possible to pass a probe right 
across the base of the skull from one sigmoid notch to the other, the shaft of the 
probe lying immediately behind the pterygoid processes of the sphenoid, and cross- 
ing the foramina ovalia, through which the inferior maxillary divisions of the fifth 
nerves pass. 
The ramus and coronoid process are so placed as to occupy a position inter- 
mediate between the zygomatic arch externally and the external pterygoid plate 
internally ; their inner surface, therefore, forms the outer wall of the zygomatic fossa. 
On a level with the surface of the crowns of the teeth of the lower jaw, and 
situated about the middle of this aspect of the ramus, is the inferior dental foramen 
(foramen mandibulare), the superior opening of the inferior dental canal (canalis 
mandibulz), which traverses the body of the bone. Through this foramen there 
pass the inferior dental branch of the inferior maxillary division of the fifth nerve, 
together with the inferior dental artery and its companion veins. As will now be 
seen, when the lower jaw is in position, the zygomatic fossa is closed in’ externally 
by the ramus of the mandible. In front there is an interval between the anterior 
border of the ramus and the zygomatic surface of the superior maxilla, through ° 
which pass the buccal branch of the fifth nerve and the communicating vein 
_ between the pterygoid plexus and the facial vein. Above, in the interval between 
the sigmoid edge and the lower border of the zygomatic arch, there pass from the 
fossa the vessels and nerves which supply the masseter muscle. Between the 
posterior border of the ramus and the styloid process there enter and leave the 
large vessels which are found within the space. Superiorly, under cover of the 
zygomatic arch, the zygomatic fossa communicates with the temporal fossa, whilst 
inferiorly it is continuous with the inframaxillary region. Internally, on the 
floor of the fossa there is an [-shaped fissure, the horizontal limb of which 
corresponds to the spheno-maxillary fissure, forming a channel of communication 
between the fossa and the orbit, through which passes the orbital branch of the 
superior maxillary division of the fifth nerve ; whilst the vertical cleft is the pterygo- 
maxillary fissure, which leads into a small fossa placed between the front of the root 
of the pterygoid process of the sphenoid and the back of the superior maxilla, called 
the spheno-maxillary fossa (fossa pterygo-palatina). 
