THE SKULL. 63 



The most marked lack of lull development is seen at 

 the junction of the frontal, coronal, and sagittal sutures, 

 Avhere a diamond-shaped or quadrilateral opening exists, 

 which does not close before the second year. 



At the junction of the sagittal and lambdoid sutures 

 is a narrow, elongated opening, caused by the divergence 

 of the posterior part of the superior borders of the 

 parietal bones, and. as before stated, it is at this place 

 principally that AVormian bones are developed. Such 

 openings are also met with at the sides of the skull, at 

 the temporo-parietal and parieto-sphenoid articulations. 

 In the infant, these openings in the skull pulsate syn- 

 chronously with the action of the heart, and hence they 

 are called fontanelles; the anterior are situated at the 

 frontal, sagittal, and coronal sutures; the posterior, at the 

 junction of the sagittal and lambdoid sutures. These 

 two fontanelles should be carefully studied, as they are 

 of great importance to the obstetrician in determining 

 the position of the head of the foetus. The internal 

 surface of the vertex is smooth, strongly concave, and 

 presents a number of slight elevations and depressions, 

 which correspond with the convolutions of the brain. 

 Running along the median line, from front to back, is 

 the groove which lodges the superior longitudinal sinus. 

 This groove is penetrated by many minute foramina, 

 which transmit veins to the sinus. Two of these, the 

 parietal, are of larger size. They are situated near the 

 posterior superior angle of the parietal bone. The 

 inner surface of the vertex also presents grooves at its 

 sides for meningeal arteries. Of these the deepest and 

 most important is that which passes up from the anterior 

 inferior angle of the parietal bone/. It lodges the middle 

 meningeal artery. 



The base of the skull presents for examination ;m 



