NORMA LATERALIS OF THE SKULL. 151 
surfaces of that process. Externally and in front, the fossa is overhung by the 
backward projection of the frontal process of the malar bone, and it is under cover 
of this, and within the angle formed by the frontal and orbital processes of the malar, 
we see the opening of the temporal canal, which pierces the orbital plate of the 
malar and transmits the temporal branch of the orbital nerve—a filament of the 
superior maxillary division of the V nerve. The fore part of the spheno-maxillary 
fissure (fissura orbita inferior) opens into the lower part of the temporal fossa, and 
thus establishes a communication between it and the orbit. If the floor of the 
fossa be carefully examined, some more or less distinct vascular grooves may 
be seen. One passing upwards over the posterior part of the squamous 
temporal, immediately in front of and above the external auditory meatus, is for 
the middle temporal artery ; two others, usually less distinct, pass up, one over the 
temporal surface of the great wing of the sphenoid, the other over the fore part of 
the squamous temporal; these are for the anterior and posterior deep temporal 
branches of the internal maxillary artery. The fossa contains the temporal muscle 
with its vessels and nerves, together with the temporal branch of the orbital nerve 
and some fat; all of which are enclosed by the fascia which stretches over the space 
from the upper temporal line above to the superior border of the zygomatic arch 
below. The extent of the fossa depends on the size of the temporal muscle, 
the development of which is correlated with the size and weight of the lower 
jaw. 
Springing from the front and lower part of the squamous temporal is the 
zygomatic process of that bone; it has two roots, an anterior and a posterior, between 
and below which are placed the glenoid fossa (fossa mandibularis) in front, and the 
opening of the external auditory meatus behind. Of compressed triangular form, the 
process at first has its surfaces directed upwards and downwards, but curving out- 
wards and forwards, it twists on itself, so that its narrowed surfaces are now turned 
outwards and inwards, and its edges upwards and downwards; passing forwards, it 
expands somewhat, and ends in an oblique serrated surface, which unites with the 
temporal process of the malar bone and completes the zygomatic arch. It is the 
upper edge of this bridge of bone which forms the posterior root. The lower border, 
turning inwards, forms the anterior root, and serves to separate the temporal from 
the zygomatic surface of the squamous temporal, blending in front with the infra- 
temporal crest on the outer surface of the great wing of the sphenoid. The under 
surface of this root is convex from before backwards, and is thrown into relief by 
the glenoid hollow, which passes up behind it. In this way a downward projection, 
which is called the eminentia articularis, is formed. 
The alar spine of the sphenoid (spina angularis) lies immediately to the 
inner side of the articular part of the glenoid fossa. Its size and projection vary. 
It is well to remember its relation to the condyle of the lower jaw when that bone 
is In position; lying, as it does, to the inner side and a little in front of that process, 
it affords attachment to the so-called long internal lateral ligament (spheno- 
mandibular) of the temporo-maxillary articulation. As will be seen hereafter, the 
anterior extremity of the osseous Eustachian canal les immediately to its inner 
side (p. 159). A noteworthy feature about the articular part of the glenoid fossa 
is the thinness of the bony plate which serves to separate it from the middle 
cranial fossa above. The vaginal process is a crest of bone which runs obliquely 
forwards from the front and inner side of the mastoid process, just below the 
external auditory meatus, to the alar spine of the sphenoid. Passing downwards 
and slightly forwards from the centre of this, and ensheathed by it in front and 
at the sides, is the pointed styloid process, the length of which is extremely variable. 
In the recess between the posterior root of the zygoma and the upper curved 
edge of the meatus there is usually a depression, though in some instances this 
may be replaced by a slight bulging of the bone. If from the posterior root of 
the zygoma a vertical line be let fall, tangential to the posterior edge of the meatus, 
a small triangular area is mapped off which has been named by Macewen the supra- 
meatal triangle. Surgically this is of importance, as it is the spot selected in which 
to trephine the bone to reach the mastoid antrum (see p. 116). 
In the suture between the posterior border of the mastoid-temporal and the 
