THE MORPHOLOGY OF THE SKULL 



121 



Turning to the base of the skull, the most striking points are the absence of the mastoid 

 processes, and the large angle which the pterygoid plates form with the skull-base, whereas in 

 the adult it is almost a right angle. The base of the skull is relatively short, and the lower 

 border of the mental symphysis is on a level with the occipital condyles. 



The facial skeleton is relatively small in consequence of the small size of the nasal fossae, 

 the small size of the maxillary sinus, and the rudimentary condition of the alveolar borders 



Fig. 144. — The Cranium at Birth. (Lateral view.) 



of the maxillae and mandible; the nasal fossae are as wide as they are high, and are almost fiUed 

 with the conchae. 



Growth takes place rapidly in the first seven years after birth. There is a second period 

 of rapid growth at puberty, when the air sinuses develop, and this affects especially the face 

 and frontal portion of the cranium. 



Fig. 145. — The Cranium at Birth in Sagittal Section. 



indicated by a *) 



(Sphenoidal concha 



(2) The Peculiarity of Individual Bones at Birth 



The occipital bone consists of four distinct parts, which have already been described. 

 Compared with the adult bone, the following are the most important points of distinction: — 

 There is no pharyngeal tubercle or jugular process; the squamous portion presents two deep 

 fissures separating the interparietal from the supra-occipital portion and extending medially 



