56 



THE STRUCTURE OF MAN 



between the parietals, assuming a markedly angular form (i.p. 

 Fig. 38, A). Although this bone persists differently in different 

 races, it is formed in the embryo from two distinct ossific centres, 



FIG. 38. A to C, VARIOUS FORMS OF THE os INCAE (interparietal bone). 

 D, E, DIAGRAM OF THE BONES OF THE OCCIPITAL REGION IN THE EMBRYO. 



(Partly after Ficalbi.) 



i.p., interparietal ; t.j.^>.,praemterparietal ; e.o., exoccipital ; s.o., supra-occipital ; b.o., 

 basioccipital ; f.m., foramen magnum. 



which, at a later stage, normally unite to form one mass with the 

 supra-occipital. This fact testifies to its paired nature, and, as 

 in the new-born child it is still separated by a cleft on each 



