Chap. IV.] 



THE SKELETON. 



35 



Fig. 27. — Frontal Bone. Outer surface. 1, frontal emi- 

 nence ; 7, roof of orbital cavity ; 10, orbital arch. 



The frontal bone resembles a cockle shell in form. It not 

 only forms the forehead, but also enters into the formation of 



the roof of the 



orbits, and of 

 the nasal cavity. 

 The arch formed 

 by part of the 

 frontal bone 

 over the eye 

 is sharp and 

 prominent and 

 affords that or- 

 gan considera- 

 ble protection 

 from injury. 

 At birth the bone consists of two pieces, which afterwards 

 become united, along the middle line, by a suture which runs 

 from the vertex of the bone to the root of the nose. This 



suture usually 

 becomes obliter- 

 ated within a 

 few years after 

 birth, but it occa- 

 sionally remains 

 throughout life. 

 The temporal 

 bones are situ- 

 ated at the sides 

 and base of the 

 skull. They are 

 named temporal 

 from the Latin 

 word, tempus, 

 time, as it is on 

 the temple the 

 hair first be- 

 comes gray and thin, and thus shows the ravages of time. 

 The temporal bones are divided into three parts : the hard, 



1 The temporal, sphenoid, lachrymal, vomer, and maxillary bones are drawn 

 to a larger scale than the other bones of the head and face. 



Fig. 28. —Temporal Bone.i 1, squamous portion; 2, 

 placed below external opening of auditory canal in petrous 

 portion : 3, placed below mastoid portion ; 4, placed below 

 glenoid cavity for reception of condyle of lower jaw. 



