THE SKELETON 59 



97. Number of Bones. There are 206 bones in the 

 adult human body. The number of bones is greatest in 

 childhood and diminishes in old age by the obliteration 

 of joints. The head has 22 bones in adult life, more in 

 infancy, and fewer in old age. 



98. General Arrangement of the Skeleton (Fig. 49). 

 The central part of the skeleton, called the vertebral or 

 spinal column, forms a firm, but flexible axis. The head 

 rests upon the top of this column. The ribs are attached 

 at its sides to make the walls of the chest. The shoul- 

 der girdle rests upon the chest, and the hip girdle is 

 attached to the base of the spinal column. These girdles 

 connect the upper and lower limbs with the trunk. 

 The bones of the head and trunk form the axial skeleton. 

 The bones of the girdles and limbs are called the ap- 

 pended skeleton, since they are appended to the axial 

 skeleton. 



99. The Skull (Figs. 51 and 52) is the cranium, or 

 casket which contains the brain, and the facial bones. 

 The arched form of the skull is the best shape for resisting 

 blows and pressure. Its bones are so firm and hard that 

 bullets sometimes glance from it. The occipital bone 

 curves under at the back of the neck to aid in forming 

 the floor of the skull. It has two projections called condyles 

 ("knuckles") situated just behind its junction with the sphe- 

 noid (" wedgelike") bone. The condyles fit into depressions 

 (Fig- 53) m the uppermost vertebra ; thus the head rests and 

 rocks upon the spinal column. Grasp the neck with both 

 hands so as to hold it motionless and stiff, and find 

 whether the head rocks forward and backward, or side- 

 wise. Between the condyles is a large opening through 

 which the spinal cord goes from the brain. 



Of the eight cranial bones, how many are in pairs, and 

 how many are not ? Those in pairs are located at the 

 sides of the cranium. The hair over the temples first 



