

THE SKULL AT BIRTH. 



195 



morphological significance, and are not more readily accounted for on the assumption 

 that they are mere irregularities in the ossification of the occluding membrane. 



The sagittal fonticulus is occasionally seen in the skull at birth as a transverse 

 fissure or angular cleft, notching the sagittal margins of the parietal bones, 

 transversely to the line of the sagittal suture, and in correspondence with the 

 position of the parietal foramina, the medial margins of which may, as yet,, be 

 unossified and formed merely by the membranous layer uniting the two bones. 

 Frequently at birth all evidence of the previous existence of this fonticulus 

 is absent. 



Most striking at birth is the occurrence of outstanding bosses, tubera parietalia, 

 on the surface of the parietal bones. These overlie the position of the primary 

 ossific centres from which these bones are originally developed, and correspond to 



Fonticulus frontalis 



Tuber frontale 



Cartilaginous 

 septum nasi 



Fossa sacci 

 lacrimalis 



Elevations corresponding 

 ?: to the position of the 

 dental sacs 



FIG. 182. FRONTAL ASPECT OF THE SKULL AT BIRTH. 



greatest maximum width of the calvaria. They mark the position of what in 

 the adult are known as the tubera parietalia, though, be it noted, that in the adult 

 i condition these reliefs need not necessarily correspond to the greater breadth of 

 :the head. 



In like manner the sites of the centres from which the lateral portions of the 

 frontal part of the frontal bone are developed are readily recognised by the presence 

 of the frontal bosses, which impart to the child's forehead its bulging appearance, 

 and correspond in later life to the position of the frontal tuberosities. As yet the 

 two halves of the frontal part of the frontal bone are ununited, being separated 

 .by the frontal or metopic suture (sutura frontalis), which lies in direct continuation 

 anteriorly with the line of the sagittal suture. The frontal suture is, as a rule, 

 more or less completely fused by the sixth year. 



The size of the infant's skull at birth varies considerably, and is to a large 



xtent dependent on the bulk and development of the child. The size of the skull 



in female infants is absolutely smaller than in the case of male children, though 



not necessarily proportionately smaller, since the weight of female children at 



irth is on the average absolutely less than male foetuses at full term. 



