When looked at from above the frontal bone is seen forming the anterior part of the vertex and articulating with the two parietals posteriorly by a nearly trans verse serrated suture (coronal suture). Running back from the middle of this is the median sagittal suture extending as far as the lambda behind. The point where the sagittal and coronal sutures join is the bregma, the site of the lozenge-shaped anterior fon tanelle in the infant's skull, but this closes during the second year of life. Small ossicles called Wormian bones are often found in the cranial sutures. About two-thirds of the way back the sagit tal suture becomes less serrated and on each side the small parietal foramen may be seen. This only transmits a small emissary vein (see VEINS) in the adult, but, as will be seen later, is of morpho logical interest. As middle life is reached, the cranial sutures tend to become obliterated and the bones can no longer be separated; this fusion begins at the places where the sutures are least deeply serrated, and as a rule the sagittal suture disappears between the two parietal foramina between thirty and forty years of age.
2).—The calvaria or brain case forms all the upper part, while the face is below the anterior half. Taking the calvaria first the side view of the frontal bone extends back as far as the coronal suture. On each side is an elevation, the frontal eminence, better seen in female than in male skulls. The junction between the frontal and malar at the outer margin of the orbit (external angular process) is an important landmark for measurements, and from it a curved line (the temporal crest) runs back crossing the coronal suture to reach the parietal bone; as it runs back this line divides into two. The quadrilateral out line of the parietal bone is seen as well as its articulations ; above it touches its fellow of the opposite side ; in front, the frontal; below, the great wing of the sphenoid or alisphenoid, the squamous part of the temporal and the mastoid part of the temporal, while behind it articulates with the supra-occipital, through the lamb doid suture. All four angles of the parietal are points of special interest ; the antero-superior angle or bregma lies nearly above the ear opening or external auditory meatus in the temporal bone. The antero-inferior angle where the frontal, parietal and ali sphenoid meet is the pterion and is the site of an occasional Wormian bone. The posterior superior angle is the lambda and is better seen behind while the posterior inferior angle, where the parietal, supra-occipital and mastoid temporal bones meet, is known as the asterion and marks the lateral sinus within the cranium. A little above and behind the middle of the parietal bone, and just above the superior temporal crest, is the parietal eminence where ossification starts. The squamous part of the
temporal bone overlaps the parietal at the squamous suture, while from its lower part the zygomatic process projects forward to ar ticulate with the malar. At the root of this process is the glenoid cavity where the condyle of the lower jaw articulates, and just behind this is the external auditory meatus. Behind this again the mastoid temporal is prolonged down into a nipple-shaped swelling, the mastoid process, containing air cells and only found in the adult human skull, while just in front of the external audi tory meatus is the styloid process, connected with the hyoid bone by the stylo-hyoid ligament (dotted). In the side view of the face the nasal and maxillary bones are seen, and from this point of view it will be noticed that just below the nasal aperture the maxillae, where they join, are produced forward into a little spur, the anterior nasal spine, which is a purely human characteristic. At the side of the maxilla the lozenge-shaped malar bone is placed ; it forms the anterior part of the zygomatic arch. When the man dible is disarticulated and removed the posterior part of the max illa is seen, and behind it the external pterygaid plate of the sphe noid. Between these two bones there is a vertical slit-like open ing into a cave, the spheno-maxillary fossa, which communicates with the orbit through the spheno-maxillary fissure, with the nasal cavity through the spheno-palatine foramen, with the cranial cavity through the foramen rotundum, and with the mouth through the posterior palatine canal, as well as having other smaller openings.
The side view of the mandible or lower jaw shows the body, and the ramus projecting up from the back part of it at an angle of from I io° to
in the adult. Before the teeth come and after they are lost the angle is greater. At the upper part of the ramus are two projections; the most anterior is the coronoid process for the attachment of the temporal muscle, while pos teriorly is the condyle which articulates with the glenoid cavity of the temporal bone.
From this point of view the posterior ends of the parietal bones, with the sagittal suture be tween them, are seen. Below these comes the supra-occipital bone separated from them by the lambdoid suture which is deeply ser rated and a frequent site of Wormian bones. Where the sagittal and lambdoid sutures meet is the lambda. In the mid line about a hand's breadth (21-3in.) below the lambda is the external occipi tal protuberance or inion, for the attachment of the ligamentum nuchae, while running out on each side from this are the superior curved lines which attach muscles of the neck.