THE SUTURES 121 



In the adult (Fig. 92) the alveolar and basilar portions of the body are usually of equal depth. 

 The mental foramen opens midway between the upper and lower border of the bone, and the 

 dental canal runs nearly parallel with the mylohyoid line. The ramus is almost vertical in 

 direction, and joins the body nearly at right angles. 



In old age (Fig. 93) the bone becomes greatly reduced in size; for with the loss of the teeth 

 the alveolar process is absorbed, and the basilar part of the bone alone remains, consequently, 

 the chief part of the bone is below the oblique line. The dental canal, with the mental foramen 

 opening from it, is close to the alveolar border. The rami are oblique in direction, the angle 

 obtuse, and the neck of the condyle more or less bent backward. 



The Sutures. 



The bones of the cranium and face are connected to each other by means of 

 sutures. That is, the articulating surfaces or edges of the bones are more or less 

 roughened or uneven, and are closely adapted to each other, a small amount of 

 intervening fibrous tissue, the sutural ligament, fastening them together. The 

 cranial sutures may be divided into three sets: (1) Those at the vertex of the skull. 

 (2) Those at the side of the skull. (3) Those at the base. 



The sutures at the vertex of the skull are four the metopic, the sagittal, the 

 coronal, and the lambdoid. 



The metopic or frontal suture (sutura frontalis) (Fig. 44) is usually noted in 

 adults as a trivial fissure, just above the glabella. At birth the two halves of the 

 frontal bone are separated by the suture. This suture is, as a rule, almost com- 

 pletely or completely closed during the fifth or sixth year, but occasionally it 

 persists throughout life. 



The interparietal or sagittal suture (sutura sagittalis) is formed by the junction 

 of the two parietal bones, and extends from the middle of the frontal bone back- 

 ward to the superior angle of the occipital. This suture is sometimes perforated, 

 near its posterior extremity, by the parietal foramen; and in front, where it joins 

 the coronal suture, a space is occasionally left which encloses a large Wormian 

 bone. 



The frontoparietal or coronal suture (sutura coronalis) (Fig. 99) extends trans- 

 versely across the vertex of the skull, and connects the frontal with the parietal 

 bones. It commences at the extremity of the greater wing of the sphenoid on one 

 side, and terminates at the same point on the opposite side. The dentations of the 

 suture are more marked at the sides than at the summit, and are so constructed 

 that the frontal rests on the parietal above, while laterally the frontal supports 

 the parietal. 



The occipitoparietal or lambdoid suture (sutura lambdoidea) (Fig. 99), so called 

 from its resemblance to the Greek letter A, connects the occipital with the parietal 

 bones. It commences on each side at the mastoid portion of the temporal bone, 

 and inclines upward to the end of the sagittal suture. The dentations of this 

 suture are very deep and distinct, and are often interrupted by several small 

 Wormian bones. 



The lateral sutures (Fig. 99) extend from the external angular process of the 

 frontal bone to the lower end of the lambdoid suture behind. The anterior 

 portion is formed between the lateral part of the frontal bone above and the 

 malar and greater wing of the sphenoid below, forming the frontomalar suture 

 (sutura zygomaticofrontalis} and frontosphenoidal suture (sutura sphenofrontalis}. 

 These sutures can also be seen in the orbit, and form part of the so-called 

 transverse facial suture. The posterior portion is formed between the parietal 

 bone above and the greater wing of the sphenoid, the squamous and mastoid 

 portions of the temporal bone below, forming the sphenoparietal, squamoparietal, 

 and mastoparietal sutures. 



