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BO^^ES. 111
faces of the face, excepting the tympanum and Eustachian tubes. These
tubes are Hned with hypoblastic tissue similar to that which lines the
alimentary canal.
The processes in front which push downward and forward are called
the fronto-nasal ; those on the side, the maxillary and mandibular.
Those which are situated deeply within the face are known as the
spheno-ethmo prolongations of the trabeculse cranii.
The changes that occur during the formative process are complex :
they produce the external nose, the lips, and the cheeks ; the mouth,
including the upper and lower jaws, the hard and soft palate ; the nasal
chambers ; the orbits ; the labyrinths ; the external auditory meatus and
tympano-Eustachian tubes ; the different air-sinuses, such as the eth-
moidal, spheno-maxillary, and frontal cells. This explains how it is
that all the facial bones proper, excepting the malar, are lined by
mucous membrane. (The special development of each bone is described
under the head General Anatomy.)
ARTICULATIONS.
When two or more bones are united together, this union is called a
joint or articulation. There are three varieties of articulation in the
head—viz. sutura, synchondroses, and diarthroses.
The Sutura are those articulations which exist between the inter-
membranous bones and also between the intermembranous and inter-
cartilaginous bones of the head. This articulation jiermits of but slight
or no appreciable movement. The bones forming this variety of articu-
lation are separated from each other by a thin layer of membrane, that
on the outer surface of the joint being derived from the pericranium,
and that on the inside from the dura mater.
There are four kinds of sutures—viz. harmonic, squamosa, dentata,
and serrata.
The Harmonic sutures are those that have comparatively smooth
articulating surfaces or borders. Examj^les, the articulation between
the palate process of the superior maxilla and the palate bones, also
the internal surfaces of the articulations of the cranial vault.
The Squamosa (squama, a scale) are those in which the opposing
surfaces of bone are bevelled, overlapping each other like the scales of
a fish. Examples, the temporo-parietal and the temporo-sphenoidal
articulations.
The Dentata {dens, a tooth) are those in which the articulating bor-
ders of the bones are severally armed with numerous tooth-like pro-
jections fitting into corresponding indentations. Example, the suture
between the two parietal bones.
The Serrata (serra, a sa^v) are those in which the articulating borders
of the bones are marked like the teeth of a saw. Example, the suture
between the two halves of the frontal bone.
The dentation and serration of the borders of the bones of the brain-
case are not marked internally, the under surface of the dome of the
skull being smooth. On the " internal surface, therefore, these sutures
^ Quain's Anatomy.
BO^^ES. 111
faces of the face, excepting the tympanum and Eustachian tubes. These
tubes are Hned with hypoblastic tissue similar to that which lines the
alimentary canal.
The processes in front which push downward and forward are called
the fronto-nasal ; those on the side, the maxillary and mandibular.
Those which are situated deeply within the face are known as the
spheno-ethmo prolongations of the trabeculse cranii.
The changes that occur during the formative process are complex :
they produce the external nose, the lips, and the cheeks ; the mouth,
including the upper and lower jaws, the hard and soft palate ; the nasal
chambers ; the orbits ; the labyrinths ; the external auditory meatus and
tympano-Eustachian tubes ; the different air-sinuses, such as the eth-
moidal, spheno-maxillary, and frontal cells. This explains how it is
that all the facial bones proper, excepting the malar, are lined by
mucous membrane. (The special development of each bone is described
under the head General Anatomy.)
ARTICULATIONS.
When two or more bones are united together, this union is called a
joint or articulation. There are three varieties of articulation in the
head—viz. sutura, synchondroses, and diarthroses.
The Sutura are those articulations which exist between the inter-
membranous bones and also between the intermembranous and inter-
cartilaginous bones of the head. This articulation jiermits of but slight
or no appreciable movement. The bones forming this variety of articu-
lation are separated from each other by a thin layer of membrane, that
on the outer surface of the joint being derived from the pericranium,
and that on the inside from the dura mater.
There are four kinds of sutures—viz. harmonic, squamosa, dentata,
and serrata.
The Harmonic sutures are those that have comparatively smooth
articulating surfaces or borders. Examj^les, the articulation between
the palate process of the superior maxilla and the palate bones, also
the internal surfaces of the articulations of the cranial vault.
The Squamosa (squama, a scale) are those in which the opposing
surfaces of bone are bevelled, overlapping each other like the scales of
a fish. Examples, the temporo-parietal and the temporo-sphenoidal
articulations.
The Dentata {dens, a tooth) are those in which the articulating bor-
ders of the bones are severally armed with numerous tooth-like pro-
jections fitting into corresponding indentations. Example, the suture
between the two parietal bones.
The Serrata (serra, a sa^v) are those in which the articulating borders
of the bones are marked like the teeth of a saw. Example, the suture
between the two halves of the frontal bone.
The dentation and serration of the borders of the bones of the brain-
case are not marked internally, the under surface of the dome of the
skull being smooth. On the " internal surface, therefore, these sutures
^ Quain's Anatomy.
