Chap. V] 



THE SKELETON 



the supraorbital margin. Just above the supraorbital margins are 

 hollow spaces called the frontal sinuses (see Fig. 33) which are 

 filled with air and open into the nose. In the upper and outer 

 angle of each orbit are two depressions called lacrimal fossae for 

 the reception of the glands of the same name, which secrete the 

 tears. At birth the bone consists of two pieces, which afterwards 

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



Fig. 24. — Occipital Bone. Inner surface. 



the vertex of the bone to the root of the nose. This suture usually 

 becomes obliterated within a few years after birth, but it occasion- 

 ally remains throughout life. 



Temporal bones. — The right and left are situated 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 becomes 

 gray and thin, and thus shows the ravages of time. The temporal 

 bones are divided into three parts — the hard, dense portion, 

 called petrous; a thin and expanded scale-like portion, called 

 squamous; and a mastoid portion, which is prolonged down- 



1 See Figs. 61 and 62. 



