OSTEOLOGY AND SYNDESMOLOGY. 19 
surface is concave and: forms part of the zygomatic fossa. Of the processes 
of this bone, the upper one is the superior orbitar. The orbitar margin 
terminates inferiorly in the inferior orbitar or angular process. The zygo- 
matic process joins the bone with the zygoma of the temporal bone; the 
maxillary bone forms a fourth angle. 
This bone articulates with the maxillary, the frontal, the sphenoidal, and 
the temporal. 
Lower jaw, maxilla inferior (pl. 123, figs. 15, 16). This bone articu- 
lates freely with the skull by means of the donllflont processes which play 
in the glenoid cavity of the temporal bone. It is distinguished into the: 
body and the branches. ‘The body consists usually of two halves, which 
are separate in the very young individual, and. unite at the anterior sym- 
physis. In the adult there are sixteen alveoli or sockets for teeth in the 
superior margin, and the portion thus occupied possesses somewhat the 
form of a horse shoe. The symphysis corresponds to the chin, mentum: 
(pl. 121, fig. 1™, fig. 4%), on each side of which is the foramen mentale 
(pl. 123, fig. 15°, pl. 121, fig. 4”); through this pass blood-vessels and a 
nerve to the face. On the inner surface, about the middle, is a small spine, 
spina mentalis interna, for the attachment of muscles of the tongue and 
larynx. The extremities of the lower jaw, ramz, are quadrilateral, and rise 
up much above the level of the body. The superior margin of each ramus 
exhibits a crescentic notch dividing it into..two portions. The anterior 
portion is triangular and slightly curved. backwards; to it is attached the 
temporal muscle, and it is known as the coronoid process (pl. 1238, fig. 15%). 
The posterior border of the notch or concavity is constituted by the 
condyloid process (jig..15*), the application of which has already been 
mentioned. On the inside of each ramus is seen the posterior mental 
foramen (jig. 16°), cca which pass the inferior maxillary vessels and. 
nerve. : 
The lower jaw is articulated with the temporal bone in such a manner 
as to admit of considerable freedom of motion in an antero-posterior and 
lateral, and still more in a vertical direction (pl. 124, figs. 1, 2,3). An inter- 
articular cartilage is placed in the joint for greater freedom of movement 
(fig. 3’). On each side of this cartilage is a synovial membrane separating 
it from the two faces of the joint. The external lateral ligament (jig. 1’) 
arises from the inferior margin of the root of the zygomatic process of the 
temporal bone, and is inserted into the neck of the condyloid process. The 
internal lateral ligament (jig. 2) arises fromthe spinous process of the 
sphenoid bone, and is inserted into the spine bordering the posterior mental 
foramen. The stylo-maxillary ligament (jigs. 1, 2, 8°) passes from the ex- 
ternal side of the styloid process, and is inserted into the posterior margin 
of the jaw, near its angle. 
C. General Considerations respecting the Head. 
The individual bones hitherto considered: constitute the head by thei 
apposition, and, as already remarked, are grouped into bones of the cranium, 
or brain ‘case. proper, and bones of the face. The cranium is an ovoidal 
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