58 EOXES OF THE HEAD. 



The interparietal, or sagittal suture, connects the two parietal bones : 

 it is continued in children, and occasionally in adults, by a suture 

 betTreeu the two halves of the frontal bone, the frontal suture. In the 

 much eloni^atcd forms of skull the sagittal suture is often found par- 

 tially or wholly obliterated by ossification. 



The temporo-parietal suture consists of two very distinct parts, the 

 squamous suture, arched in direction, in which the scale-like margin of 

 the squamous portion of the temporal bone OA'erlays the similar margin 

 of the parietal, and the 2)aricto-mastoid suture, which is thick and 

 serrated. 



The spJiono-parietal suture, between the parietal bone and great 

 wing of the sphenoid, is about half an inch in extent. It is absent 

 only in very rare cases, and then the frontal and temporal bones come 

 into contact. 



The name of transir?ve lias by some anatomists been given to the series of 

 sutures which unite the facial and orbital marg-ins of the frontal to other bones, 

 as the malar, sphenoid, ethmoid, lachrymal, maxillary, and nasal. The lines of 

 union between the other bones, though more or less serrated, have not received 

 any special designation, but may be named from the bones between which they 

 nm, as for example, petro-occipital, petro-sphenoidj inter-maxillary, palato- 

 pterygoid, &c. 



Ossa Triquetra. — Separate pieces of bono are found in many skulls, intei-posed 

 between the cranial bones. They are called ofisa trujiietra. ossa Wonni'i, ossa 

 sutnrarum, kc. They are of ii-regular form, with margins adapted to the cha- 

 racter of the sutm-es in which they are situated. They are most frequently found 

 in the occipito-parietal suture, where they occur sometimes in great numbers, 

 more or less symmetrically aiTanged ; in other instances, one or several bones of 

 considerable size may occupy the place of the superior part of the occipital, and 

 may con-espond to the interparietal bone of some an i mala. They are much less 

 frequently found in the other sutui-es, 



EXTERNAL SURFACE OF THE SKULL. 



The external surface of the skull may be conveniently divided into 

 superior, inferior, anterior, and lateral regions. 



The superior region, extending from the supra-orbital ridges in 

 front to the superior curved line of the occipital bone behind, and 

 bounded laterally by the temporal ridges, is smooth and convex, covered 

 only by the integument and by the muscular fibres and fascia of the 

 occipito-frontalis muscle. It is of an oval form, broader in the parietal 

 than the frontal region, flattened in front, and projecting somewhat in 

 the middle behind. There is also a slight projection from the general 

 curve at each of the frontal and parietal eminences. 



Tlie anterior region of the skull, below the forehead, presents the 

 openings into the orbits, bounded hy the frontal, malar, and superior 

 maxillary bones ; and between the orbits, the bridge of the nose, 

 formed by the nasal bones and ascending processes of the superior 

 maxillaries. Below the nasal bones is the nasal aperture, of an inverted 

 heart shape : its thin margin gives attachment to the nasal cartilages, 

 and projects forwards in the middle line below as the nasal spine. 

 Below the nasal aperture are the incisor foss^ of the upper jaw ; 

 below the orbits are the canine fossa3 ; and external to the canine fossas 

 are prominences of the cheeks, formed by the anterior inferior parts 

 of the malar bones. The lower jaw completes the skeleton of the face. 



