FRONTAL AND OCCIPITAL BONES 



21 



third of each margin is a supraorbital notch (sometimes foramen) 

 for the supraorbital nerve, artery, and vein. Just above the 

 margins are the superciliary arches, which bear the eyebrows and 

 mark the position of spaces in the frontal bone called the frontal 

 sinuses. These sinuses begin to develop at the age of seven years 

 and grow larger as time advances. They communicate with the 

 nose, and contain air. The smooth space between the eyebrows 

 is the glabella. 



The nasal part is just below the glabella. 



The orbital parts (or plates) of the frontal bone are so called 

 because they are hi the roof of 

 the orbits, or eye-sockets; the 

 space between these parts is 

 occupied by the ethmoid bone 

 and is called the ethmoid notch. 

 Just underneath the lateral part 

 of the superior margin of the 

 orbit is a small fossa (the lacri- 

 mal fossa), containing the lacri- 

 mal gland, where the tears are 

 formed. 



At birth the frontal bone is 

 in halves right and left 

 which become united in early 

 life. 



Occipital bone (os occipitale). At the back of the skull and 

 consisting of two portions: squamous (scale-shaped) and basal 

 (Figs. 12 and 21). 



The squamous portion (squama occipitalis) is flat in structure, 

 triangular in shape, and joined to the parietal bones. The most 

 prominent point on the back of the skull is on this portion, and 

 is called the occipital protuberance or inion. 



The basal portion bends forward, extending far enough toward 

 the front to form the roof of the throat. This portion presents a 

 large opening called the foramen magnum (or great foramen), 

 which transmits the spinal cord*. At the sides of the foramen 

 magnum are two smooth prominences, called the occipital condyles, 

 which rest upon the first bone of the spinal column, whereby the 

 nodding movement of the head is permitted. 



FIG. \$. FRONTAL BONE, SHOWING 

 THAT IT ORIGINATES IN HALVES. 

 (Morris.) 



