230 



THE SKELETON 



The Appejtdiculae Skeleton'. 



The pectoral girdle. — Attention has been called to the 

 fact that the ends of two bones called the collar bones 

 (clavicles) fit into the notches at the top of the sternum. 

 These bones may be readily located by the fingers in front 

 and on each side of the neck. These bones extend from 

 the sternum to the shoulders, where their ends form part of 

 the socket for the upper arm bone. The other parts of 

 the socket are formed by two large, triangular bones which 



Fig. 89 — The pectoral girdle ; a, backbone ; b, scapula ; c, shoulder joint ; d, arm 

 bone ; e, clavicle ; /, rib ; g, breastbone (sternum). 



fit against the back and are held in place by muscles and 

 ligaments. These triangular bones are called the shoulder 

 blades, or scapulas (see Fig. 89) . The scapulas, clavicles, 

 and the upper arm bones on each side of the body meet at 

 a common point (the shoulder joint), and the only attach- 

 ment of these three bones to the axial skeleton is the place 

 where the clavicles are jointed to the sternum. Such an 

 arrangement permits of great play to the arms and shoul- 

 ders. Since the arrangement of clavicles and scapulars is 

 such as to encircle the upper part of the thoracic cavity, 

 these four bones are called the pectoral girdle. 



The pelvic girdle. — On the sacrum arc two large facets, 

 or surfaces, to which are attached, one on each side, two 



