54 SUTURES OSSA TRIQUETRA. 



SUTURES. 



The bones of the cranium and face are connected with each 

 other by means of sutures (sutura, a seam), of which there are four 

 principal varieties, serrated, squamous, harmonia, and schindylesis. 



The serrated suture is formed by the union of two borders pos- 

 sessing serrated edges, as in the coronal, sagittal, and lambdoid 

 sutures. In these sutures the serrations are formed almost wholly 

 by the external table, the edges of the internal table lying nearly in 

 apposition. 



The squamous suture (squama, a scale) is formed by the over- 

 lapping of the bevelled edges of two contiguous bones, as in the 

 articulation between the temporal and lower border of the parietal. 

 In this suture the approximated surfaces are roughened, so as to 

 adhere mechanically with each other. 



The harmonia suture (f 5 to adapt) is the simple apposition of 

 contiguous surfaces, the surfaces being more or less rough and re- 

 tentive. This suture is seen in the connexion between the superior 

 maxillary bones, or of the palate processes of the palate bones with 

 each other. 



The schindylesis suture (otyviJuXrjrfj?, a fissure) is the reception of 

 one bone into a sheath or fissure of another, as occurs in the articu- 

 lation of the sphenoid with the vomer, or of the latter with the per- 

 pendicular lamella of the ethmoid, and with the palate processes of 

 the superior maxillary and palate bones. 



The serrated suture is formed by the interlocking of the radia- 

 ting fibres along the edges of the flat bones of the cranium during 

 growth. When this process is retarded in the infant by over-dis- 

 tention of the head, as in hydrocephalus, and sometimes without 

 any such apparent cause, distinct ossific centres are developed in 

 the interval between the edges; and, being surrounded by the 

 suture, form independent pieces, which are called ossa triguetra, or 

 ossa Wormiana. In the lambdoid suture there is generally one or 

 more of these bones ; and, in a beautiful adult hydrocephalic 

 skeleton in the possession of Mr. Listen, there are upwards of one 

 hundred. 



The coronal suture (fig. 23) extends transversely across the 

 vertex of the skull, from the upper part of the greater wing of the 

 sphenoid to the same point on the opposite side ; it connects the 

 frontal with the parietal bones. In the formation of this suture the 

 edges of the articulating bones are bevelled, so that the parietal 

 rest upon the frontal at each side, and in the middle the frontal rests 

 upon the parietal bones, so as to afford each other mutual support 

 in the consolidation of the skull. 



The sagittal suture (fig. 23) extends longitudinally backwards 

 along the vertex of the skull, from the middle of the coronal to the 

 apex of the lambdoid suture. It is very much serrated, and serves 

 to unite the two parietal bones. Sometimes this suture is continued 



