502 



MAMMALIAN ANATOMY 



FIG. 404. 



The subsequent growth of the 

 skull from forty-four clays to adult 

 life is marked by an increasing den- 

 sity of the bones and by a change 

 in form, produced by the relatively 

 greater increase in the length of the 

 face and a relative decrease in the 

 length and height of the cranium. 



The scrolls of the lateral ethmoid 

 increase in size and complexity, and 

 the ossification in the mesethmoid 

 extends gradually forward. 



In some specimens the upper 

 posterior part of the lachrymal does 

 not ossify ; the lateral ethmoid is 



FIG. 405. 



THE SKULL, FORTY-FOUR DAYS AFTER BIRTH. 

 (Natural size.) 



then uncovered and forms the os 

 planum. 



The table on page 506 contains 

 principally such measurements of 

 the skull as exhibit the relative 

 sizes of the cranium and face at 

 the different ages already studied. 

 They were taken upon longitudi- 

 nally bisected skulls as follows : 



The distance from the opisthion, 

 on the posterior margin of the fora- 

 men magnum, to the alveolar point, 

 at the middle of the anterior edge 

 of the premaxillary alveolar border, 

 is the length of the cranial and 

 nasal cavities. 



The long diameter of the cranial 



THE SKULL, SIXTY DAYS AFTER BIRTH. 

 (Natural size.) 



