42 ANATOMY FOR NURSES. [CHAP. IV. 



rising like the water in a fountain. There are six of these 

 fontanelles. The anterior fontanelle is the largest, and is a 

 lozenge-shaped space between the angles of the two parietal 

 and two frontal bones. The posterior 

 fontanelle is much smaller in size, and 

 is a triangular space between the occip- 

 ital and two parietal bones. The other 

 ( A four fontanelles, two on each side of 

 the skull, are placed at the inferior 

 angles of the parietal bones : they are 

 unimportant. T]^e posterior fontanelle 

 is closed by an extension of the ossify- 

 ing process a few months after birth. 



FIG. 44. THE SKULL AT ,-., . . ,., ,, 



BIRTH. Superior surface, i, The anterior remains open until the 

 posterior fontanelle; 2, sagit- sec ond year, and occasionally persists 



tel suture ; 4, anterior f on- i , -i / mi i , i in 



taneiie; A, A, bi-parietai throughout lite. I he base of the skull 

 diameter; B, B, bi-temporai j s mucn thicker and stronger than the 



walls and roof ; it presents a number 



of openings for the passage of the cranial nerves, blood-ves- 

 sels, etc. 



The diameters of the foetal skull given by King are : 



Occipito-mental (from posterior fontanelle to chin) . . 5-|- inches. 

 Occipito-frontal (centre of frontal bone to occiput) . . 4|- inches. 

 Bi-parietal (from one parietal prominence to another) . 3^- inches. 



The fcetal cranial bones being imperfectly ossified, and their 

 edges separated by membranous intervals, they are readily 

 moulded, and they overlap one another more or less during 

 parturition. 



The pelvic cavity. The pelvis, so called from its resemblance 

 to a basin, is stronger and more massively constructed than 

 either the cranial or the thoracic cavity. It is composed of 

 four bones, the ossa innominata forming sides and front, and 

 the sacrum and coccyx, completing it behind. It is divided 

 by a brim or prominent line, the linea ilio-pectinea, into the 

 false and true pelvis. The false pelvis is all that expanded 

 portion of the pelvis situated above the brim : it forms an in- 

 complete or " false " basin. The true pelvis is all that portion 

 situated below the brim. Its cavity is a little wider in every 



