The Framework of the Body 



35 



51. The Shoulder and Arm. The two 



bones of the shoulder, the scapula and 



the clavicle, serve to attach the arm to 



the trunk. 



The scapula, or shoulder-blade, is a 



flat, triangular bone, lying on the upper 

 and back part of the 

 chest, over the ribs. 

 It consists of a broad, 

 flat portion and a 

 prominent ridge or 

 spine. At its outer 

 angle it has a shallow 

 cup known as the glen- 

 oid cavity, in which 

 plays the rounded head 

 of the humerus. 



The clavicle, or collar 

 bone, so named from 

 its resemblance to an 

 ancient key, is a slen- 

 der bone with a double 

 curve like an italic /. 

 It extends horizontally 

 from the shoulder- 



FIG ' 2 r Left Clavicle, b , ade {o thg breast . 

 or Collar Joone. 

 (Anterior surface.) bone - I{ thuS 



serves, like the 



keystone of an arch, to hold the 

 shoulder-blade firmly in its place. 

 Its chief use is to keep the shoulders 

 wide apart, that the arm may enjoy 

 a free range of motion. This bone FIG. 21 



Left Humerus. 



