MUSCLES. 



39 



to turn the hand, palm downwards. This is done (Fig. 16) 

 by rolling the lower end of the radius, which carries the 

 hand, around the ulna. When the palm is upward the 

 radius and ulna lie side by side as shown at A\ while it 

 is being turned downward, the lower end of the radius 

 rolls around the ulna and at 

 last crosses it to get on its *' 

 inner side, as shown at B. 



7. The Muscles of the human 

 body are more than five hun- 

 dred in number. They vary in 

 size from tiny ones inside the 

 ear, not half an inch long, to 

 that (29,Plate II.) which passes 

 from the pelvis to the tibia and 

 is eighteen inches or more in 

 length. All muscles have the 

 power of shortening and thus 

 of pulling other parts (usu- 

 ally bones) to which their 

 ends may be attached. After F,Gi6.-Bones of the forearm 



111 j j a d hand. A, the palm turned 



a muscle has shortened and forwards or upwards <**///), 



. . 1-11 and the radius and ulna parallel; 



done Its WOrk, It lengthens B, the palm turned downwards or 



. backwards (pronation), and the ra- 



agam, or relaxes. In addition dius crossing the ulna. 



to their chief function of moving the body, muscles 



clothe the skeleton and make the form round and 



shapely; they aid in enclosing cavities, as the mouth 



and abdomen; and they help to hold bones together at 



joints. 



7. How many muscles in the body ? Their size? On what do our 

 movements depend ? What other functions have muscles ? 



