44 



ANATOMY FOE NUKSES. 



[CHAP. IV. 



period of foetal life. Before birth the bones at the top and 

 sides of the skull are separated from each other by membra- 

 nous tissue in which bone is not yet formed. The spaces 

 at the angles of the bone occupied by this membranous tissue 

 are termed the fontanelles, so named from the pulsations of 

 the brain, which can be seen in some of them, rising like the 

 water in a fountain. There are six of these fontanelles. The 



FIG. 44. THE SKULL, a, nasal bone ; b, superior maxillary ; c, inferior maxillary; 

 d, occipital; e, temporal; /, parietal; g, frontal bone. 



anterior fontanelle is the largest, and is a lozenge-shaped space 

 between the angles of the two parietal bones and the two 

 segments of the frontal bone. The posterior fontanelle is 

 much smaller in size, and is a triangular space between the 

 occipital and two parietal bones. The other four fontanelles, 

 two on each side of the skull, are placed at the inferior angles 

 of the parietal bones : they are comparatively unimportant. 

 The posterior fontanelle is closed by an extension of the ossify- 

 ing process a few months after birth. The anterior remains 



