22 STRUCTURE OF THE HUMAN BODY 



has but one bone, the humerus. The forearm contains 

 two bones, the ulna and the radius. The expanded end 

 of the ulna forms the elbow joint, into which the radius 

 enters only with its small tip. At the wrist, on the 

 contrary, the expanded end of the radius makes up most 

 of the joint, the ulna in turn entering with its small end. 

 This arrangement permits the extensive rotation of the 

 hand Avhich is most important for its free use. 



Wrist. The wrist is made up of a number of irregu- 

 larly shaped block-like bones. They are small and 

 are knit together by strong ligaments, so that they 

 give considerable freedom of movement without loss 

 of strength. 



Hand. The palm of the hand is formed of five slender 

 bones, which lead from the wrist bones to the roots 

 of the fingers. The first of these is tipped with two 

 fairly stout bones, which form the thumb. Each of 

 the remaining four bones carries three slender bones, 

 which form the fingers. 



The hand of man resembles that of the higher apes 

 much more closely than does his foot, but it is supe- 

 rior to theirs in the position and flexibility of the thumb. 

 To this, man owes a part of the power of delicately 

 handling objects, which characterizes the use of his 

 hands. 



Pelvic girdle. The pelvic girdle consists of two broad 

 flaring bones which in front are joined together by liga- 

 ments and behind are also firmly connected by ligaments 

 to the sacrum. In young children, as in many of the 

 lower vertebrates, each of these two bones consists of 

 three distinct bones. Their union gives a much firmer 

 support for the legs and trunk. 



Leg. The legs are attached to the pelvic girdle by 

 means of the hip joints. Each leg consists of two main 



