32 ANATOMY AND PHYSIOLOGY 



THE SKULL AT BIRTH 



The bones are only partially developed, a considerable space 

 between them being occupied by membrane (in some places, 

 cartilage), and the frontal bone is in two pieces. 



Fontanelles. The parietal and Jrontal bones are incomplete 

 at the angles where their sutures meet, leaving a diamond-shaped 

 space above the forehead where there is membrane only, and which 

 is called the anterior or frontal fontanelle. The parietal and 

 occipital bones also are lacking where their sutures meet, leaving 

 a triangular soft spot called the posterior or occipital fontanelle, 

 which is much smaller. These fontanelles are closed as the bones 

 develop; the occipital in a few months, the frontal before the end of 

 the second year. 



Superciliary 

 ridge 



Glabella 



FIG. 24. THE OKBIT. (After Morris.) 



Obstetric note. Owing to the fact that the bones are not 

 firmly jointed, they can be made to overlap and thus adapt the 

 shape of the child's head to the passage which it must traverse 

 during birth. This is called the moulding of the head (Figs. 22 

 and 23). 



The four large fossae of the exterior of the skull are the tem- 

 poral, infratemporal, orbital, and nasal. 



The temporal fossa (fossa temporalis}. The thinnest part 



