THE SKELETON 



227 



and irregular and provide many places for the attachment 

 of muscles and ligaments. Each innominate bone has a 

 deep, round socket into which the end of the femur (the 

 long bone of the leg) accurately fits. 



5. The Arm and PI and Groups. A long bone, the hu- 

 merus, connects the arm with the shoulder and gives form 

 to the upper arm. In the forearm are two bones, the radius 

 and the ulna, which connect at one end with the humerus 

 and at the other with the bones of the wrist (Fig. 102). 



A group of eight small, round bones is found in the 

 wrist, known as the carpal bones. These are arranged in 

 two rows and are movable upon one another. Five straight 

 bones, the metacarpals, 

 connect with the wrist 

 bones and form the 

 framework for the palm 

 of the hand. Attached 

 to the metacarpals are 

 the bones of the fingers 

 and thumb. These form 

 an interesting group of 

 fourteen bones, called 

 the phalanges of the 

 fingers (Fig. 102). 



The bones of the hand 

 provide a mechanical 

 device, or machine, for 

 grasping, and the arm 

 serves as a device for moving this grasping machine from 

 place to place. The work of the arm, in this respect, is 

 not unlike that of a revolving crane upon the end of which 

 is a grab-hook. The hand without the arm to move it 

 about would be of little use. 



Patella 



r etatarsus 

 SI 



Phalanges 

 FIG. 102. Bone groups of arm and leg. 



