132 OSTEOLOGY. 
As viewed from the outer side, the bone is convex from side to side and has 
four angles, of which three are prominent. These are the ascending or frontal 
(processus fronto-sphenoidalis), the anterior or pointed extremity of the maxillary 
border, and the posterior or temporal (processus temporalis). 
The most elevated part of the convex outer surface (facies anterior) forms the 
malar tuberosity. The processus temporalis, sometimes called the zygomatic process, 
ends posteriorly in an oblique edge, which articulates with the extremity of the 
zygomatic process of the temporal bone. The frontal, the most prominent of its 
processes, is united superiorly to the external angular process of the frontal bone. 
The edge between the frontal and temporal processes is thin and sharp; it affords 
attachment to the temporal fascia, and near its upper end there is usually a 
pronounced angle (processus marginalis), formed by a sudden change in the direc- 
tion of the line of the bone. It is just below this point that the temporal branch of 
the orbital nerve becomes cutaneous. The lower border of the temporal process is 
somewhat thicker and rounded; it extends downwards and forwards towards the 
inferior angle, where the bone articulates with the superior maxilla, and is then 
confluent with the ridge which separates the facial from the zygomatic aspect of 
Frontal process Frontal process 
] 
Orbital border 
_~ Malar canal Orbital process 
Temporal 
Temporal Malar canal y process 
process 
\f> Maxillary 
border 
\. Tem poro- 
zygomatic 
surface 
For articulation 
with superior 
maxilla 
Masseteric 
border 
Fic, 103.—RicHtT Matar Bone. A, Outer Side; B, Inner Side. 
the upper jaw. This edge of the bone is sometimes called the masseteric border 
since it affords attachment to the fibres of origin of the masseter muscle. Sweeping 
downwards in front of the frontal process is a curved edge which terminates 
inferiorly in a pointed process. This border forms the outer and, in part, the 
inferior margin of the orbital cavity. Between the anterior extremity of the 
masseteric edge and the pointed anterior angle there is an irregular suture by 
which the bone is joimed to the maxilla. The opening of the malar canal (foramen 
zygomatico-faciale) is seen on the outer surface of the bone; its size and position 
are very variable. 
The mesial aspect of the bone is distinguished by a curved elevated crest, called 
the orbital process, which extends inwards and backwards, and is confluent externally 
with the orbital margin. This process has two surfaces—one anterior, which forms 
a part of the outer and lower wall of the orbit, and one posterior, which is directed 
towards the temporal fossa above and the zygomatic fossa below. The free edge 
of the orbital process is thin and serrated; a little below its middle it is usually 
interrupted by a non-articular notch, which corresponds to the anterior extremity 
of the spheno-maxillary fissure. The part above this articulates with the great wing 
of the sphenoid, the portion below with the orbital plate of the superior maxilla. 
Behind the orbital process, the inner surface of the bone is concave from side to 
side, and extends backwards along the mesial aspect of the temporal process and 
upwards over the posterior half of the inner side of the frontal process, thus 
entering into the formation of the zygomatic and temporal fosse respectively. 
The orbital surface of the orbital process usually displays the openings of two 
canals (foramina zygomatico-orbitalia)—one which traverses the bone below the 
orbital margin and appears on the front of the bone as already described, the other 
