THE SUTURES AND FONTANELLES. 83 



THE SUTURES AND FONTANELLES. 



Name the Sutures of the skull. There are 17. 

 At the Vertex of the skull are 5, the 



Sagittal, or interparietal. 



2 Coronal, or fronto-parietal. 2 Lambdoid, or occipito-parietaL 

 At the Sides of the skull are 4, the 



2 Spheno-panetal. 2 Temporo-parietal. 

 At the Base of the skull are 5, the 



2 Temporo-occipital. Basilar, in the central line of the base. 



2 Temporo-sphenoidal. 

 In the Mesial line, besides the sagittal and basilar, are 3, the 



Spheno-ethmoidal. Spheno-frontal. Ethmo- frontal. 



Describe the Facial Sutures. The most important are the following, but 

 the sutures of the face are very numerous. 



Zygomatic Suture, at the temporo-malar articulation. 



Transverse Suture, extending from one external angular process of the 

 frontal bone across to the other, and connecting that bone with the malar, 

 sphenoid, ethmoid, lachrymal, superior maxillary, and nasal bones. 



Symphysis of the Chin, the site of a foetal suture. 



How are the Sutures formed ? By dentations of the external tables in- 

 terdigitating with each other, the adjacent edges of the internal tables lying in 

 unjoined proximity. The sutures are not formed until a long time after the 

 formation of the skull, probably to permit of the marginal growth of the bones. 



What are the Fontanelles ? They are 6 membranous intervals in the in- 

 fant's skull, corresponding in situation with the angles of the two parietal 

 bones. They are as follows, viz. 



Anterior, at the junction of the sagittal and coronal intervals. 



Posterior, at the junction of the sagittal and lambdoid intervals. 



Lateral Fontanelles, 4, two at the anterior inferior angles, and two at the 

 posterior inferior angles of the parietal bones. 



Describe the Wormian Bones. They are supernumerary small pieces 

 of bone, irregularly shaped, and developed by special centres in unclosed por- 

 tions of the cranial sutures and fontanelles, being more frequent in the lamb 

 cloid suture. They are also called "ossa triqueta" from their triangular form. 



Describe the Hyoid Bone. It is shaped like a horse-shoe, has no articu- 

 lation with the skeleton, but supports the tongue. It consists of a Body, two 

 greater, and two lesser Cornua or horns. On the body is a Crucial Ridge, 

 with a Tubercle at the centre. It is developed"^ 5 centres, one for the body 

 and one Tor each horn. Attached to it are lo muscles, 3 ligaments, and J 

 membrane, as follows, viz. 



c 



