30 OUR BODIES AND HOW WE LIVE 



47. The Bones of the Shoulder and Arm. There are two 

 bones in the shoulder, and they serve to fasten the arm to 

 the trunk. These are the scapula, or shoulder blade, and 

 the clavicle, or collar bone. 



The shoulder blade is a large, flat, three-sided bone, which 

 is placed on the upper and back part of the chest. On the 

 outer side it has a saucerlike cavity on which the rounded 



head of the arm bone rests. 



The collar bone is a long, nar- 

 row bone, with a double curve 

 like the italic letter/. It serves, 

 like the keystone of an arch, to 

 keep the shoulders wide apart, 

 and thus to allow the arms great 

 freedom of movement . Its inner 

 end is tied to the breastbone, 

 and its outer to the shoulder 

 blade. 



The humerus, a long, hollow 

 bone, rests against a shallow 



The Scapula. ^^ ^ ^ shoulder bhde 



It is joined at the elbow to the bones of the forearm. 



48. The Bones of the Forearm. The forearm contains 

 two long, hollow bones, the ulna and the radius. 



The ulna, or elbow bone, is the larger of these two bones. 

 It is joined to the humerus by a hinge joint at the elbow. 

 It is on the same side as the little finger. 



The radius, queerly named because it is supposed to 

 resemble one of the spokes of a wheel, is the long, slightly 

 curved, outer bone of the forearm. It is on the same side 

 as the thumb. Its upper end is fastened both to the ulna 

 and the humerus. 



